Zbigniew Kalbarczyk and his future wife Regina Osiej hid more than ten Jews in their flats in Warsaw. From 1940, Regina hid three people and Zbigniew - four. As many as eleven people lived in the flat of Adela Kalbarczyk, Zbignew's deceased mother.
In 1943, Zbigniew and Regina got married and started to live at 23 Tamka Street. They also had flats at 22 6 Sierpnia, 51 Dobra and 3 Radzymińska Streets. During the German occupation period, they cooperated with the Central Welfare Council and the Jewish National Committee. Through a Jewish female liaison called Borman (Dworakowska), they received money passed by the Jewish underground to support Jews hiding on the so-called Aryan side. Due to underground secrecy requirements, the rescuers knew little about some of the people that were hidden and supplied with food. Kalbarczyk recalls Sylwia (or Krystyna), who was hidden in Dobra Street, Zofia Kwiatkowska with her son Stanisław in Tamka Street and Kozłowska, who was hidden in Słowackiego Street.
In his 1983 account presented at the Jewish Historical Institute in 1983, Zbigniew Kalbarczyk described the support offered to Jews between 1939 and 1945. The document included a short description of the aid offered by himself and his wife during the war as well as a list of 17 men, women and children supported by them. As Kalbarczyk stressed: “The help that I and my wife Regina offered to the Jewish population consisted in hiding people in our own flats, transporting them to a place of residence, searching for flats, buying and supplying food to them, passing money from the Welfare Council and taking out the deceased from the flats."
According to Cristine Szenberg's account (born as Krystyna Gutfrajnd), she and her mother and sister were "taken over from the sewers" by Kalbarczyk after the suppression of the Warsaw ghetto uprising. The woman and her daughters were hidden in a flat at 22 6 Sierpnia Street. The Wizenbergs with their fifteen-year-old son Józef were hidden in a flat owned by the Kalbarczyks’ at 51 Dobra Street. According to Kalbarczyk's 1986 account, Aron Wizenberg was to have been killed in as a combatant in Podwale Street. From 1941, Regina Kalbarczyk also hid Maria and Juliusz Zakrzewski. According to Cristina Szenberg's account, they died when a building collapsed during the Warsaw Uprising. Artur Hejtler, another hiding Jew, also died during the occupation.
Of those hidden by the Kalbarczyks, the following people survived: Regina Heytler (probably Hejtler), liaison Wolman vel Bregman with her daughter Zofia, sisters Krystyna and Barbara Gutfrajnd and Józef Wizenberg. After the war, Józef went to Israel and the Gutfrajnd sisters – to France.
In 1983, the Gutfrajnd sisters presented their account of the selfless help offered to Jews by the Kalbarczyks at the Yad Vashem. Cristina Szenberg stressed in her account, also signed by her sister: "I was treated as a family member - I owe my life to them." In 1984 the Yad Vashem Institute decided to grant Regina and Zbigniew Kalbarczyk the title of Righteous Among the Nations.
In a 1993 letter to the Province Office in Warsaw, Zbigniew bitterly noted: "We saved the lives of 18 Jews during the Holocaust - today we receive no financial aid from people who, if they are still alive, do not help us."