To explore further the report of an accelerated weight gain following termination of treatment with a stimulant drug, 66 biannual growth measurements were obtained from 1970 to 1973 on hyperactive schoolchildren who were receiving medication. All received either dextroamphetamine or methylphenidate during the school year; some also received it during the summer. The data revealed that those whose stimulant medication was terminated at the start of summer subsequently grew in weight and height at a significantly greater rate than those who continued to receive medication from June to September. In fact, discontinuance of the medication resulted in a growth rebound for this period which was 15-68% above the age-expected increment.