Although placebo controls and double-blind conditions are considered to be essential for the unbiased scientific assessment of drug effects, there is very little research on these procedures in the pediatric psychopharmacology literature. To examine the impact of controlled assessment procedures on the magnitude of observed drug effects, two groups of children with attention-deficit hyperactivity disorder (ADHD) were evaluated for response to methylphenidate under two different assessment procedures. One group (n = 33) was part of a placebo-controlled, double-blind crossover research protocol, with randomized dose sequences, compliance checks, numerous dependent measures, written informed consent, and a considerable amount of staff involvement. The other group (n = 43) received pharmacotherapy at a community-based child psychiatry outpatient service where they were followed in a routine clinical manner, with "no treatment" as the only control condition, standard fixed-dose titration, parental responsibility for data collection, use of form letters, and minimal staff involvement. Each individual in both groups received divided doses of 0.3 and 0.5/0.6 mg/kg daily for a minimum of 1 week at each dose. Comparisons of teacher ratings obtained for the two assessment procedures revealed highly similar findings. The results of this study are discussed with regard to both their methodological and clinical implications.