Cocaine was involved in 66 cases (39 homicides, 27 accidental overdoses), methamphetamine in 32 cases (23 homicides, 9 accidental overdoses), and a combination of cocaine and methamphetamine in 10 cases (4 homicides, 6 accidental overdoses). The composite for cocaine-related deaths was a 30-year-old Black man in whom was also found at least one other drug, usually ethanol or morphine. The composite for methamphetamine-related deaths was a 32-year-old Caucasian man who used methamphetamine with at least one other drug (usually ethanol). For cases involving both cocaine and methamphetamine, the composite was a 36-year-old Caucasian man in whom was also found at least one other drug, usually ethanol, codeine, or morphine. Mean tissue concentrations of cocaine and benzoylecgonine were significantly higher in accidental overdoses than in homicides except for cocaine concentrations in liver, which did not differ significantly between the two groups. For methamphetamine-related deaths there was no significant difference between mean tissue concentrations in accidental overdoses and in homicides. Cocaine or methamphetamine or both were involved in approximately one-third of homicides in San Diego County in 1987, and when fatal accidental overdoses were included, cocaine was involved in twice as many cases as methamphetamine. (Author abstract)