The short-term dose effects of methylphenidate were examined on cardiovascular measures in 11 black male adolescents diagnosed as having attention deficit hyperactivity disorder (ADHD). In a double-blind, cross-over design with randomized order, the subjects received placebo and each of three methylphenidate doses (0.15, 0.3, and 0.5 mg/kg) for a period of 2 weeks per medication dosage. Significant main effects were found for diastolic and systolic blood pressure; however, pairwise comparisons revealed a significant linear increase in diastolic blood pressure only. Because of the unexpected increase in diastolic blood pressure, careful monitoring of black adolescents who are receiving methylphenidate is recommended.