Twenty-one hyperactive children received in turn 500 mg. caffeine, 300 mg. caffeine, and 20 mg. methylphenidate per day in a double-blind cross-over design investigation. Each drug was given for three weeks. Methylphenidate resulted in significantly improved behavior in the children as rated by mothers and teachers and as indicated on tests of impulsivity and motor control. There were no significant improvements with either of the caffeine tests, although some children showed slight improvements with caffeine. The negative effects with both caffeine and methylphenidate were minimal.