Objective: To evaluate the features and modes of adaptation to aging among Methadone Maintenance Treatment (MMT) enrollees.Setting: Beth Israel Medical Center in New York City.Participants: A sample of 156 MMT enrollees (103/66 percent males and 53/34 percent females) age 24-68 years. Twenty-nine percent of participants were aged 55 or older.Design: A cross-sectional, multivariate, correlational design.Outcome Measures: Participants were administered the MMSE, ASI, BSI, as well as measures of impulsiveness and quality of life (QOL).Results: Older adults were more likely to have had longer periods of treatment (p < 0.01), less likely to report current heroin use (p < 0.05) and overall drug use (p < 0.05), but were more likely to have a history of comorbid alcohol misuse (p < 0.01). Advanced age was also associated with less impulsiveness, hostility, paranoia, and interpersonal sensitivity (p < 0.01), more chronic medical problems (p < 0.05), greater use of medication for medical problems (p < 0.05), and more liberal take home medicine schedules (p < 0.01). However, no differences were found between older and younger participants with respect to their scores on the Overall Social Support scale (p > 0.05), the Personal Well-Being Index (p > 0.05) and the Satisfaction with Life Scale (p > 0.05), suggesting comparable levels of QOL. Furthermore, the rate of contact for older participants with medical professionals did not differ significantly from that of younger participants (p > 0.05). Only 7.1 percent of older participants reported regular contact with a primary care physician; a rate that is slightly lower than the rate in the overall population.Conclusions: The findings from the present study highlight at least two underappreciated challenges that clinicians are increasingly likely encounter in their work with the aging MMT population. These challenges are: (1) that despite numerous medical and psychiatric complaints, only a small proportion of MMT patients have regular contact with a primary care physician and the rate of contact does not appear to increase with age and (2) even with age-related declines in psychiatric comorbidity and illicit substance use, the suboptimal level of QOL that is characteristic of the MMT population as a whole does not improve with aging and length of tenure in MMT.