A 10-year review of the records of the King County Medical Examiner's Office (Washington State) found that of 87 deaths due to necrotizing fasciitis and related necrotizing soft-tissue infection, 32 of the 64 cases with sufficient information for analysis were determined to be due to injection of black tar heroin. Of these 32 cases, 24 were clostridial infections (particular category of bacteria) with various species represented. Of the 32 cases of necrotizing fasciitis and related necrotizing soft-tissue infections unrelated to the injection of black tar heroin, streptococcal species of bacteria predominated. Only three of the 32 cases not associated with black tar heroin injection were clostridial infections. These differences were statistically significant, supporting the conclusion that necrotizing fasciitis due to black tar heroin injection is primarily a clostridial disease, which distinguishes it from necrotizing fasciitis due to other causes. Since these infections are a potential cause of death in drug users and other individuals coming under the jurisdiction of medical examiners and coroners, it is important for death investigators and forensic pathologists to be aware of necrotizing fasciitis and its association with black tar heroin injection, particularly in jurisdictions of the Northwest where black tar heroin is virtually the only form of heroin used. 2 tables and 17 references