The use of the recreational drug crystal methamphetamine among younger homosexual men is expanding, and with it, unsafe sex behaviors that increase the transmission of human immunodeficiency virus (HIV). This article reviews available literature on the medical and psychiatric morbidities associated with methamphetamine abuse in HIV-infected patients. Medical complications include hypertension, hyperthermia, rhabdoymyolysis, and stroke. One fatal case of ingestion of methamphetamine with HIV medication has been documented. Two fatal cases of ingestion of HIV medication with the amphetamine analogue n-methyl-3,4 methylenedioxymethamphetamine (MDMA, or "ecstasy") have also been reported. Some molecular researchers suggest that dopaminergic systems are vulnerable to the combined neurotoxicity of HIV infection and methamphetamine. Population surveys indicate high rates of HIV infection among methamphetamine abusers and high rates of unprotected anal intercourse during drug intoxication. Intoxication can sometimes produce paranoia, auditory hallucinations, and, occasionally, violent behavior. Amphetamine withdrawal commonly results in symptoms of depression. Methamphetamine is a new challenge related to treatment and prevention of HIV infection.