In a recent review, Hattie, Sharpley, and Rogers (1984) concluded that patients treated by paraprofessional therapists improve more than those treated by professionals. However, this provocative conclusion is based on inappropriate studies and statistical analyses. The present review omitted problematic studies and organized the data to permit valid statistical inference. Unlike Hattie et al., we found that professional and paraprofessional therapists were generally equal in effectiveness. Our analyses also suggested that professionals may be better for brief treatments and older patients, although these differences were slight. Current research evidence does not indicate that paraprofessionals are more effective, but neither does it reveal any substantial superiority for the professionally trained therapist.