This article analyzes the relationship between rumors about the Holocaust and the process of the formation of knowledge about the Shoah among ordinary residents and public opinion in the Warsaw ghetto during World War II. Rumor is defined here as a specific medium, encumbered with a high risk of distortion, but still sometimes carrying true information. I analyzed war-time personal documents and testimonies of survivors. I focused in particular on rumors regarding the extermination of Jews in other towns and letters that were supposedlyreaching the Warsaw ghetto from residents deported purportedly to the East, but who wereactually murdered in the Treblinka death camp. To interpret this phenomenon, I used theoretical approaches from the social sciences (awareness context theory and symbolic interactionism theory). I stressed the impact of the existential experience of Shoah victims on their ability to accept the news of mass murder. Special attention was paid to the process of pushing aside thoughts about the possibility of one’s own death.