Clindamycin 450 mg every 8 hours for 3 days cured three non-immune patients of falciparum malaria, although the response was slow. The addition of quinine to this regimen provided an accelerated response and cured 3 of 5 other patients. Single doses of clindamycin given daily for 3 days, with or without quinine, cured 1 of 3 patients. Gastric intolerance to the drugs, probably accentuated by the clinical condition, was pronounced in some cases, the course of treatment being interrupted in three patients for this reason. Chesson strain Plasmodium vivax relapses in man were not inhibited by ingestion of 450 mg of clindamycin every 6 hours for 14 days.