Access to antiretroviral treatment (ART) has improved greatly in many parts of the world, including Uganda, yet, many patients delay to start ART even when registered within the HIV services. We assessed, in a routine ambulatory care setting, what proportion of patients start ART late and the associated factors. We conducted a cross-sectional study from a cohort of adult, HIV-infected, ART-naive patients seeking care at 3 primary care centers in Kampala, Uganda. ART eligibility at the time was World Health Organization clinical stage 4 or CD4 <200 cells/μL. We defined late start of ART as starting ART at CD4 count <100 cells/μL and analyzed associated factors using multivariable logistic regression. Between May 2008 and August 2009, 326 adults were studied. Two hundred eighteen (67%) were women; the median age was 34 years (range, 18-71). The median CD4 count was 132 cells/μL (range, 1-505). Thirty-one patients (10%) were in World Health Organization stage 4. One hundred twenty-three patients (37.7%) were initiated on ART with CD4 cells <100 cells/μL. Being male [adjusted OR (aOR): 2.4; 95% confidence interval: 1.3 to 4.2, P = 0.002] and having no employment (aOR: 1.9; 95% confidence interval: 1.2 to 3.3, P = 0.012) were associated with late start of ART. Being older, being married, and showing signs of alcohol dependence were associated with an earlier start of ART. A considerable proportion of patients started ART at very low CD4 counts. Male and unemployed patients were more likely and married people and those aged 40 years or older were less likely to start ART late.