Carmustine or BCNU (bis-chloroethylnitrosourea) is a mustard gas-related β-chloro-nitrosourea compound used as an alkylating agent in chemotherapy. As a dialkylating agent, BCNU is able to form interstrand crosslinks in DNA which prevents DNA replication and DNA transcription. It has the appearance of a orange-yellow solid. Carmustine for injection is marketed under the name BiCNU by Bristol-Myers Squibb.