This research investigation was undertaken in an effort to discern possible differences between three comparative groups of methadone maintenance applicants on the basis of sample background characteristics, type of presenting psychopathotogy, and severity of psychiatric disturbance. The findings revealed a broad spectrum of' psychiatric disturbance among the three comparative groups {Mexican-American males, Caucasian males, and females). More psychiatric disturbance was detected within the mate samples. Over hatfofthe entire population studied manifested moderate to severe psychiatric disturbances. The results of this research are discussed in view of the implications for rehabititation, treatment planning, and staffing composition within a methadone maintenance program.Within recent years, responsibility for treatment of the compulsive narcotics user has gradually been shifted from the province of the Federal government to the local community. A number of conceptually distinct treatment approaches or models have been developed on the premise that different approaches may be more effective and have more relevance for specific addicts than others.Emphasis upon generating a multimodality system has gained increasing popularity. This view has come to imply that within a treatment network a wide range of treatment modalities should be offered. Commonly utilized approaches are methadone maintenance, the self-regulating therapeutic community (residential treatment), and traditional methods (often, abstinence and either individual or group therapy).A determination of the nature and extent of personality dysfunction or psychopathology in narcotic dependent individuals is a necessity if a scientific foundation for treatment approaches is to exist. This factor becomes particularly relevant in that a wide range of psychotropic drugs, behavioural, and psychotherapeutic techniques exist which are fairly specific in their approach to symptom reduction and behavioural change.The extent and nature of psychopathology present among narcotic users is vital to the design of an efficient rehabilitation program and has profound implications for the staffing composition of the treatment program as well as for the specific therapeutic interventions which might be employed.