The conviction rates for the first 61 admissions to a therapeutic community for drug dependence were obtained for a period of 2 years prior to admission and two years after discharge, by searching in the Criminal Records Office at Scotland Yard. A long-stay group of 20 which had remained in residence more than 6 months was compared with a medium-stay group of 20 which had remained from 1 to 6 months and a short stay group numbering 21 which had remained less than 1 month. The long-stay group had a preadmission conviction rate of 60 percent, which was significantly reduced to 10 percent during the followup period. The conviction rate of the medium-stay group was reduced from 70 percent before treatment to 45 percent after treatment; that of the short-stay group remained constant at 57 percent before and after treatment. It is suggested that periods of more than 6 months, treatment in the community are effective in reducing subsequent criminality. Further work is necessary in order to determine the relationship between treatment, background factors and subsequent criminality. Eleven references and four tables are provided. (Author abstract modified.)