In order to evaluate the efficacy of biofeedback for childhood encopresis, 50 children with encopresis were prospectively studied and randomized to receive biofeedback (B) or mineral oil therapy (M). Specificity of biofeedback was also evaluated by comparing outcomes of both regimens in children with normal (n = 32) and abnormal (n = 18) defecation patterns. Using a single blinded design, there were no significant differences in clinical outcomes between the 24 children receiving B and the 26 children receiving M at 3, 6, and 12 months. However, at 12 months six of nine children with abnormal defecation patterns were in remission or markedly improved after receiving B, compared to only three of nine children receiving M. In contrast, children with normal patterns appeared to respond better to M than did those receiving B (71 vs. 40% at 12 months). Biofeedback appears to warrant further evaluation in children with encopresis and abnormal defecation patterns.