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He pulled out an old picture of his brother as a lieutenant in the Soviet Army. Then, choking up, he showed a prewar picture of three primly dressed sisters and a brother, all under 12 at the time. All four died in the war.

After immigrating to New York, Mr. Rozenkier served in the Korean War, earning two Bronze Stars, and then spent 20 years working in Manhattan's garment district. After the war, he and his wife, Joan, were often invited to reunions of death camp survivors.

''I felt like a jackass,'' he said. ''I'd go there, and they all had three or four kids and I didn't have any. I was walking around like an outcast.''

Monographs by Nazi doctors and numerous books and treatises have described the sterilization work at labs run by Dr. Mengele and others. Chemicals were injected into the uterus of hundreds of Jewish and Gypsy women, causing blockages in their fallopian tubes that rendered them sterile. The Nazi doctors also X-rayed male inmates to sterilize them, but the X-rays often killed the men or caused such severe burns that they became unfit for work. Mr. Rozenkier said that this must have led the Nazis to begin experimenting with chemical sterilization on men.

Mr. Rozenkier was one of several thousand victims who survived the experiments. Robert Jay Lifton, author of ''The Nazi Doctors,'' said, ''Certainly there was widespread sterilization and castration, and all this was part of a distorted racial vision that sought to destroy the capacity to reproduce in ostensibly inferior races and especially Jews.''

Mr. Rozenkier was born in Wroclawek, Poland, 75 years ago. In September 1939, soon after Hitler invaded Poland, German soldiers pounded on his family's apartment door to arrest Mr. Rozenkier's father. When his oldest sister, Helena, stepped outside to protest, a soldier shot her to death.

Wroclawek's Jews were sent to a ghetto on the outskirts of town. Mr. Rozenkier escaped, and for several months slept in a cemetery next to an aunt's grave.

He was arrested when he was 14 and sent to a work camp. There, he loaded sand, nearly died of typhus and was eventually assigned the job of carting away hundreds of Jews who had died of typhus.

One day while transporting the dead he visited a Polish family to beg for potatoes. German soldiers seized him and planned to hang him, but he was spared because the commander of a nearby women's work camp put in a good word for him. Breaking into tears, he said: ''My sister, Leah, worked for that commander. She was his cook. But she sold her body to him to save my life.''

After more than a year in work camps, he was shipped to Auschwitz in a crammed cattle car. He was tattooed with the number 143511 and assigned to a nearby work camp that made synthetic rubber. One day, an associate of Dr. Mengele saw him and had him sent to the nearby Birkenau camp for experiments.

With reddish-blond hair that made him look less Jewish, Mr. Rozenkier said, he was spared from the gas chamber because the Nazi doctors thought he had unusual genes. He said, ''They were trying to figure out why this Jew got red hair.''

At Birkenau, while many were starving around him, Mr. Rozenkier was fed an ample diet of buckwheat to help him survive the experiments.

''Sometimes they even gave us chocolate -- can you believe it? Chocolate,'' he said.

''Mengele didn't give a damn if I live or die,'' he continued. ''Sometimes he gave people a piece of chocolate, and the next minute he shoots them in the head.''

After Mr. Rozenkier survived the sterilization shots, a doctor who took a liking to him arranged for him to work in a coal mine. From there, he joined the infamous death march to Buchenwald in which the Nazis shot hundreds of stragglers. He was in Buchenwald when American troops liberated it.

Had he known that he was sterile, he said: ''I never would have married my wife. It's not fair to her. She's entitled to have children.'' They adopted a daughter, Allison, who is now 35.

Mr. Rozenkier is seeking money from Schering and Bayer, which was then a division of I. G. Farben, because records show that doctors from Schering participated in the sterilization work at Birkenau and other camps, while drugs Bayer developed were used in sterilizations. His lawsuit also wants the companies to disclose which chemicals were injected into him.

In his eyes, the lawsuit is a way to achieve justice. He says he will donate any money he wins to Israel.

Like many Holocaust survivors, Mr. Rozenkier feels uneasy that he lived while so many family members and other Jews perished. ''I'm the only one who suffers right now because I should have been with them,'' he said. ''I feel guilty.''

Photos: Mr. Rozenkier, 75, at his home on Staten Island. (Photo by Richard Perry/The New York Times); Simon Rozenkier, third from left in a dark cap, on the day the Buchenwald concentration camp was liberated in 1945. (Photo by Margaret Bourke-White/Time-Life/Getty)