The authors conduct an evaluation of a middle school-based treatment program for youth with ADHD during early stages of treatment development. The studies focus on interpreting outcome trends in preliminary data and identifying assessment issues that will be important to consider when conducting a clinical trial. Parent reports indicate that the majority of students benefit from improvements in academic, social, and overall functioning. Although teachers report beneficial effects for the majority of the participants in the program, there is little agreement about individual students. Measurement problems are associated with understanding normal change during a school year, accounting for normal behavior changes in December and May, and considerable disagreement between teachers. Suggestions to guide future work in this area are provided. (Contains 2 tables and 2 figures.)