This study evaluated Trypanosoma cruzi parasitemia in persons with chronic Chagas disease, compared the parasitemia in human immunodeficiency virus (HIV)-positive and -negative subjects, and, for HIV-positive subjects, analyzed the association between parasitemia and occurrence of acquired immunodeficiency syndrome-defining illnesses, CD4 cell counts, HIV loads, and antiretroviral therapy. In total, 110 adults with chronic Chagas disease (29 HIV positive, 81 HIV negative) were studied. T. cruzi parasitemia was evaluated by xenodiagnosis, blood culture, and direct microscopic examination of blood. T. cruzi parasitemia was detected significantly more frequently in HIV-positive than in HIV-negative subjects (odds ratio, 12.3; 95% confidence interval, 3.7-41.2). HIV-positive patients also had higher levels of parasitemia. No statistically significant association was seen between parasitemia and the variables of interest among the HIV-positive subjects.