Objective: To determine whether methylphenidate (MPH) and mixed salts amphetamine (MSA) have different effects on growth in children with attention-deficit/hyperactivity disorder. Method: Patients treated for at least 1 year with MPH or MSA were identified. A linear regression was performed to determine the effect of stimulant type, patient gender, cumulative stimulant dose, and length of time in treatment on change in Z scores for height. A subset of patients was identified who had 3 years of consistent stimulant treatment on either MSA or MPH. Repeated-measures analyses of variance were performed to examine the effects of time and medication type on Z scores for weight, height, and body mass index. Results: The linear regression showed no effect of stimulant type, drug holidays, or length of time of treatment on change in height Z score. Cumulative dose of stimulant had a small (-0.26) relationship to change in height Z scores. For patients treated for 3 years, there were no effects of stimulant or time on height Z scores. MSA produced more decrease in weight and body mass index Z scores than MPH; all of the subjects were heavier than average at baseline. Conclusion: MSA and MPH did not differ in their effects on height. MSA had more of an effect on weight than MPH, although the effect was modest in magnitude and may be of limited clinical significance. (Contains 5 figures and 1 table.)