The structure of the Outcome Questionnaire-45 (Lambert et al., 2001) was examined in a sample of 1,100 university counseling center clients using confirmatory factor analysis. Specifically, the relative fit of 1-factor, 3-factor orthogonal, 3-factor oblique, 4-factor hierarchical, and 4-factor bilevel models were examined. Although the 3-factor oblique, 4-factor hierarchical, and 4-factor bilevel models fit the data well, the 4-factor bilevel model fit the data best. The results provided support for the fit of the 4-factor bilevel model where each item loads on 1 of the 3 independent scales of Symptom Distress, Social Role Performance, and Interpersonal Relations, in addition to a nonoverlapping general distress factor. (Contains 3 figures, 2 tables and 2 footnotes.)