We present a case in which suicide was a severe neuropsychiatric reaction to treatment with mefloquine. Physicians must be aware of these serious psychiatric complications and bear them in mind when faced with atypical behavior or suspected suicide. The body of a 27-year-old man was discovered at his home, covered with multiple knife wounds. The autopsy report concluded that death was due to a craniocerebral wound from a violent blow. Homicide was initially suspected. Suicide during acute psychosis associated with mefloquine was suggested, and toxicologic analyses confirmed this hypothesis. Serious neurologic and psychiatric adverse events associated with mefloquine (Lariam) have been reported since its introduction in 1985. Mefloquine prophylaxis is recommended for travelers to high-risk areas of chloroquine-resistant plasmodium falciparum. The risk of malarial infection and the proven efficacy of mefloquine to prevent malaria should be weighed against the risk of drug-associated adverse events. Physicians must nonetheless be aware of these serious psychiatric complications, especially when faced with atypical behavior and atypical suicides. The patient's' family and friends should be asked about a possible trips abroad that might have entailed antimalaria treatment, even several months earlier. Testing for mefloquine during toxicological examinations is then essential. The World Health Organization recommendations and contraindications must be followed in prescribing mefloquine.