Methylphenidate (Ritalin) hydrochloride, a CNS stimulant, is being used with increasing frequency in children with the hyperkinetic syndrome. More than 150,000 children were treated in 1973 and this number is increasing rapidly.1 Recent reports have noted a slowing of growth in hyperactive children given stimulant drugs. Safer et al2-4 noted a retardation in both weight and height increase in 63 hyperactive children who were given either dextroamphetamine or methylphenidate for two years. Additionally, they noted that 13 of these children had a rebound weight gain with discontinuation of dextroamphetamíne therapy, a "less striking" growth suppression only when dosages of greater than 20 mg daily of methylphenidate were used. They also noted that increasing the dosage of stimulant used over time generally increased the degree of growth suppression.3-4 Weiss et al5 reported no deleterious effect of methylphenidate on growth. Schain and Reynard6 reported that 40% of the