The toxicities of cocaine are far-ranging. They include sudden death, acute medical and psychiatric illness, infectious complications, reproductive disturbances, trauma, criminal activities and societal disruption, including child neglect and abuse and lost job productivity. This chapter focuses on the medical complications. Medical complications in general reflect the intense sympathomimetic activities of cocaine ('sympathetic neural storm'). Psychiatric complications include acute anxiety or panic and paranoid psychosis. Cardiovascular complications include arrhythmias and sudden death, acute myocardial infarction, myocarditis, dissecting aneurysm and bowel infarction. Neurological complications include seizure, intracerebral haemorrhage and brain injury due to hyperthermia and/or seizures, and headache. The incidence of medical complications has been estimated using two databases collected prospectively in the United States. In 1989 and 1990 cocaine ranked first in total encounters, major medical complications and drug-related deaths. An attempt was made to assess the intrinsic toxicity of cocaine by computing the incidence of adverse health outcomes per population of drug abusers. Rates of emergency department visits and deaths were 15.1 and 0.5 respectively, per 1000 persons using drugs in the past year. The magnitude of the cocaine problem, while considerable, is relatively small compared with that of cigarette smoking or alcohol abuse.