The antimalarial chloroquine is a widely used medication prescribed for a variety of conditions. The authors indicate that its lethality and behavioral side effects are significant and may be underestimated. Moderately low overdosage of chloroquine can result in rapid death. Moreover, therapeutic doses are known to cause psychosis, delirium, personality changes, and depression. It is hypothesized that a drug-induced alteration of mood or a toxic confusional state may result in unintended overdosage and death. Clinicians should consider prodromal signs of toxicity and not classify overdosage prematurely as attempted self-poisoning.