This dissertation had three specific aims: to estimate the prevalence of adherence among drug users, to determine whether drug use was directly associated with adherence, and to assess whether factors drawn from the Behavioral Model of Health Care Utilization (BMHCU) are associated with adherence. The self-reported prevalence of adherence to prescribed health care recommendations in the past 12 months among the community sample of drug users and non-drug users from similar low-income areas in the study sample ranged from 53%-74%. Non-drug users consistently had higher rates of adherence than drug users, except for adherence to female health care recommendations, yet this difference was insignificant at the bivariate level. In the multivariate analysis, when controlling for all other variables within the BMHCU, only non-injection drug use was significantly associated with adherence to mental health care recommendations. In exploring its predictive utility, the BMHCU accounted for a range of 17% to 54% of the variance for the adherence measures. Although percentages accounted for by the BMHCU were substantial the fact that very few predictor variables were significant may indicate multicollinearity and other severe limitations with the data, such as small sample size, and the conceptualization of the adherence measure. The conceptualization of adherence remains an issue in need of further delineation. Further studies are needed in order to develop appropriate measures of adherence. Qualitative studies may be needed to further understand adherence among drug users.