In addition to overdose, withdrawal, and addictive behavior, licit and illicit drugs produce a wide range of neurologic complications. Trauma results from intoxication and from violence related to a drug's illegality. Infection, including AIDS, is most often a consequence of parenteral use. Seizures can be secondary to either toxicity or withdrawal. Stroke can be ischemic or hemorrhagic. Persistent cognitive dysfunction affects alcoholics and probably users of other drugs as well. Teratogenicity is better documented for ethanol and tobacco than for illicit drugs. Other complications of recreational drug use include peripheral neuropathy, myelopathy, parkinsonism, leukoencephalopathy, optic atrophy, and cerebellar ataxia.