Compared the scores obtained on the Omnibus Personality Inventory by groups of relatively effective and relatively ineffective counselor trainees. The trainees (61 students in their 1st yr of a counseling psychology program) completed the tests prior to their 1st practicum experience and were evaluated by their practicum supervisors (PhD or master's-level counselors with more than 5 yrs of experience at supervision) at the end of each of their practica. Ss were classified as relatively effective, relatively ineffective, or indeterminant ^h (ns = 32, ^H 30, and 12, respectively) on the basis of their practicum supervisor's evaluations. The scores of the relatively effective and relatively ineffective trainees were compared using 1-way analyses of variance. Data revealed significant differences in the personality characteristics of the groups. The relevance of these findings for the selection of counselor trainees is discussed.