The research sample for the current study numbered 231 males, which included 48 pedophiles, 39 exhibitionists, and 144 assaulters. The followup study, begun in 1979, was designed to evaluate the long-term effects of group psychotherapy and intensive probation supervision on the sex offense recidivism rates of sex offenders. The research design permits assessment of the comparative effectiveness of the two intervention strategies; intensive probation supervision only and group psychotherapy with probation. The probation-only group qualifies more as a comparison group than as a control group; however, through the random assignment procedure, other differences between the two groups were controlled. The purpose of the 10-year followup study was to assess the effectiveness of the two intervention strategies by a comparative analysis of sex offense recidivism rates for both groups. For all 231 men, 148 in group psychotherapy and 83 on probation only, 26 (11.3 percent) were rearrested on a subsequent sex offense. Twenty men (13.6 percent) in group psychotherapy recidivated, and six men (7.2 percent) in the probation-only group recidivated. A comparison of these groups and subsequent sex offense recidivism reveals, however, no statistically significant difference for the two intervention strategies. Cautions in interpreting these findings are discussed, and tabular data and 10 footnotes are provided.