To identify sociodemographic, clinical, and pharmacological factors  associated with nonadherence to antiretroviral treatment in patients with  human immunodeficiency virus/acquired immunodeficiency syndrome treated  between 2017 and 2020 in four cities in Colombia. An observational, cross-sectional, retrospective study was conducted of a population of patients with human immunodeficiency virus/acquired immunodeficiency syndrome treated between 2017 and 2020. The Morisky-Green scale, the simplified medication adherence  questionnaire, and the simplified scale to detect adherence problems to  antiretroviral treatment were applied to determine patient adherence. A  binomial multiple logistic regression was performed to evaluate the factors that  best explain nonadherence. A total of 9,835 patients were evaluated, of whom 74.4% were men,  71.1% were aged between 18 and 44 years, 76.0% had attended at most  secondary school, 78.1% were single, and 97.6% resided in an urban area.  After applying three different scales to each patient, 10% of the study  population were identified as nonadherent to treatment. The risk of  nonadherence was significantly higher in patients who presented any drug- related problem or had an adverse reaction to antiretroviral drugs. The variables most strongly associated with nonadherence to  antiretroviral treatment were drug-related problems, adverse drug reactions, a  history of nonadherence to treatment, and psychoactive substance use.