A drug used to treat certain types of brain tumors. It is also used with prednisone to treat multiple myeloma and with other drugs to treat Hodgkin lymphoma and non-Hodgkin lymphoma that have not gotten better with other treatment or have come back. It is also being studied in the treatment of other types of cancer. BCNU damages the cell's DNA and may kill cancer cells. It is a type of alkylating agent and a type of nitrosourea.