The objectives of the study were to evaluate the general reactions of probation officers and probationers to the collection of hair samples, to compare the outcomes of the hair samples with the outcomes of urinalyses (which the probationers undergo routinely), to note and react to differences in the prevalence as indicated by the two assay types, and to assess the general monitoring potential for hair assays in a correctional setting. In general, hair assays showed an increased capability of detecting cocaine exposure when compared to urinalysis; the detection of cannabis was problematic for hair. Collection of hair samples was not difficult and cooperation of the probationers was quite good. Probation officers appeared to prefer the use of hair specimens to urine specimen collection, and appeared enthusiastic about the potential use of hair analysis in their routine monitoring of clients, The article includes discussion of the possible interpretation of study outcomes as they bear on the potential utility of hair analysis in various field settings. Tables, references, appendix