In a suburban methadone program, using official police records, a study was made of patients' arrest records before and after methadone treatment. Eighty patients were willing to allow the researchers to secure their arrest records. These 80 patients were similar to the total clinic population of 226 in terms of demographic variables, arrest record, and addiction history. For these 80 patients both the rate of arrest and the number of patients arrested declined in association with entering methadone maintenance treatment. The decline was statistically significant for drug-related offenses but not for nondrug-related offenses. Overall, the decline in both rate of arrest and number of patients arrested was significant, but this was due to the decrease in drug-related arrests.Drug-related arrests play a dominant role in the criminality of the suburban patients in this study. Because of this, the reduction in drug-related arrests is more significant for this group of patients than it would have been for an inner-city patient population.