Highly active antiretroviral therapy (HAART) has proved effective in prolonging survival and improving the quality of life of the people living with HIV/AIDS (PLWHA). For the successful treatment of HIV infection, at least 95% adherence to HAART is required. This study sought to assess adherence to HAART and to identify factors enhancing adherence within the study population. The study was a descriptive cross-sectional survey of 428 patients attending the antiretroviral (ARV) clinic of the Federal Medical Centre, Makurdi. Self-reported adherence and other data were collected using an interviewer-administered questionnaire. Data were analysed using SPSS 11.0 and Epi6; and were exported into Systat 11 for multivariate logistic regression. There were 151 (35.3%) males and 277 (64.7%) females. The mean age was 36.7 +/- 9.6 years. Self-reported adherence rate was 268 (62.6%). The factor most predictive of adherence to HAART was availability of ARVs [OR = 5.2; 95% confidence interval 3.1-8.6; p < 0.001], followed by the ability to afford regular visits to the ARV clinic [OR = 1.7; 95% confidence interval 1.04-2.8; p = 0.034]. A recent diagnosis of HIV made less than 3 years prior to the study period was also significantly associated with adherence to HAART (chi2 = 8.94; p = 0.003). Availability of ARVs and ability to afford to regularly visit the clinic among other factors, positively influenced adherence to HAART among PLWHA. Efforts should be targeted at constant provision of free ARVs and early initiation of therapy for those requiring treatment, as well as ensuring regular adherence-education.