The present article describes and evaluates the Youth Counseling Impact Scale (YCIS; L. Bickman et al., 2007), a recently developed therapeutic process measure that assesses youths' perceptions of the impact individual mental health counseling sessions have on their thoughts, feelings, and behaviors. This measure is intended for frequent use in the mental health treatment of youths aged 11-18. It provides a general Impact score as well as two subscale scores: Insight and Change. Five hundred youths receiving mental health services participated in this investigation. Classical test theory, item response theory, confirmatory factor analysis, and analyses of the relationship of the YCIS with other scales were used to evaluate the research questions. The results suggest that, overall, the YCIS is a well-functioning scale with good psychometric properties. The proposed model for 1 primary general factor of impact and 2 secondary factors (Insight and Change) fit the data well. Specific weaknesses of the scale are discussed, and possible improvements are suggested. (Contains 3 figures, 6 tables and 3 footnotes.)