Neighborhood characteristics associated with negative reaction to community-based methadone maintenance treatment programs (MMTPs) were studied using the MMTPs in Brooklyn, Bronx, Manhattan, and Queens (71 census tracts). A measure of community opposition to the establishment of the clinics was developed (CRMC). Census and survey data were combined for data analysis. Results are presented following a fourfold conceptual framework focused on the community's social ecology, patient characteristics, clinic administration, and the physical ecology of the clinic location. Eight specific characteristics found within these four conceptual areas accounted for 49% of the variation in CRMC.