A History of Mengele's Gruesome Experiments on Twins

Twin sisters Yehudit and Lea Csengeri playing together outside.
Twin sisters Yehudit and Lea Csengeri were taken to Auschwitz and injected with various pathogens. United States Holocaust Memorial Museum / Courtesy of Yehudit Csengeri Barnea

From May 1943 until January 1945, Nazi doctor Josef Mengele worked at Auschwitz, conducting pseudo-scientific medical experiments. Many of his cruel experiments were conducted on young twins.

Notorious Doctor of Auschwitz

Portrait of Nazi Medical Officer Joseph Mengele
Bettmann Archive / Getty Images

Mengele, the notorious doctor of Auschwitz, has become an enigma of the 20th century. Mengele's handsome physical appearance, fastidious dress, and calm demeanor seemingly contradicted his attraction to murder and gruesome experiments.

Mengele's seeming omnipresence at the railroad unloading platform called the ramp, as well as his fascination with twins, incited images of a mad, evil monster. His ability to elude capture increased his notoriety as well as gave him a mystical and devious persona.

In May 1943, Mengele entered Auschwitz as an educated, experienced, medical researcher. With funding for his experiments, he worked alongside some of the top medical researchers of the time.

Anxious to make a name for himself, Mengele searched for the secrets of heredity. The Nazi ideal of the future would benefit from the help of genetics, according to Nazi doctrine. If so-called Aryan women could assuredly give birth to twins who were sure to be blond and blue-eyed, the future could be saved.

Mengele, who worked for Professor Otmar Freiherr von Vershuer, a biologist who pioneered twin methodology in the study of genetics, believed that twins held these secrets. Auschwitz seemed the best location for such research because of a large number of available twins to use as specimens.

The Ramp

Mengele took his turn as the selector on the ramp, but unlike most of the other selectors, he arrived sober. With a small flick of his finger or riding crop, a person would either be sent to the left or to the right, to the gas chamber or to hard labor.

Mengele would get very excited when he found twins. The other SS officers who helped unload the transports had been given special instructions to find twins, dwarfs, giants or anyone else with a unique hereditary trait like a club foot or heterochromia (each eye a different color).

Mengele was on the ramp not only during his selection duty but also when it was not his turn as a selector to ensure twins would not be missed. 

As the unsuspecting people were herded off the train and ordered into separate lines, SS officers shouted in German, "Zwillinge!" (Twins!). Parents were forced to make a quick decision. Unsure of their situation, already being separated from family members when forced to form lines, seeing barbed wire, smelling an unfamiliar stench -- was it good or bad to be a twin?

Sometimes parents announced they had twins, and in other cases relatives, friends, or neighbors made the statement. Some mothers tried to hide their twin, but the SS officers and Mengele searched through the surging ranks of people in search of twins and anyone with unusual traits.

While many twins were either announced or discovered, some sets of twins were successfully hidden and walked with their mother into the gas chamber.

About 3,000 twins were pulled from the masses on the ramp, most of them children; only around 200 survived. When the twins were found, they were taken away from their parents.

As the twins were led away to be processed, their parents and family stayed on the ramp and went through selection. Occasionally, if the twins were very young, Mengele would allow the mother to join her children for their health to be assured for the experiments.


After the twins had been taken from their parents, they were taken to the showers. Since they were "Mengele's children," they were treated differently than other prisoners. Though they suffered through medical experiments, the twins were often allowed to keep their hair and allowed to keep their own clothes.

The twins were then tattooed and given a number from a special sequence. They were then taken to the twins' barracks where they were required to fill out a form. The form asked for a brief history and basic measurements such as age and height. Many of the twins were too young to fill the form out by themselves so the Zwillingsvater (twin's father) helped them. (This inmate was assigned to the job of taking care of the male twins.)

Once the form was filled out, the twins were taken to Mengele. Mengele asked them more questions and looked for any unusual traits.

Life for the Twins

Each morning, life for the twins began at 6 o'clock. The twins were required to report for roll call in front of their barracks no matter what the weather. After roll call, they ate a small breakfast. Then each morning, Mengele would appear for an inspection.

Mengele's presence did not necessarily cause fear in the children. He was often known to appear with pockets full of candy and chocolates, to pat them on the head, talk with them, and sometimes even play. Many of the children, especially the younger ones, called him "Uncle Mengele."

The twins were given brief instruction in makeshift "classes" and were sometimes even allowed to play soccer. The children were not required to do hard work and had jobs like being a messenger. Twins were also spared from punishments as well as from the frequent selections within the camp.

The twins had some of the best conditions at Auschwitz until the trucks came to take them to the experiments.


Generally, every day, every twin had to have blood drawn.

Besides having blood drawn, the twins underwent various medical experiments. Mengele kept his exact reasoning for his experiments a secret. Many of the twins that he experimented on weren't sure for what purpose the individual experiments were for or what exactly what was being injected or done to them.

The experiments included:

  • Measurements: The twins were forced to undress and lie next to each other. Then every detail of their anatomy was carefully examined, studied, and measured. What was the same was deemed to be hereditary and was different was deemed to be the result of the environment. These tests would last for several hours.
  • Blood: Blood tests included mass transfusions of blood from one twin to another.
  • Eyes: In attempts to fabricate blue eyes, drops or injections of chemicals would be put in the eyes. This often caused severe pain, infections, and temporary or permanent blindness.
  • Shots and Diseases: Mysterious injections caused severe pain. Injections into the spine and spinal taps were given with no anesthesia. Diseases, including typhus and tuberculosis, would be purposely given to one twin and not the other. When one died, the other was often killed to examine and compare the effects of the disease.
  • Surgeries: Various surgeries were performed without anesthesia including organ removal, castration, and amputation.
  • Death: Dr. Miklos Nyiszli was Mengele's prisoner pathologist. The autopsies became the final experiment. Nyiszli performed autopsies on twins who had died from the experiments or who had been purposely killed just for after-death measurements and examination. Some of the twins had been stabbed with a needle that pierced their heart and then was injected with chloroform or phenol, which caused near immediate blood coagulation and death. Some of the organs, eyes, blood samples and tissues would be sent to Verschuer for further study.