Highly active antiretroviral therapy (HAART) has changed the epidemiology of Pneumocystis jiroveci pneumonia (PCP) in AIDS patients. Global incidence of PCP has decreased and now it is prevalent in AIDS patients who do not receive HAART or are unsuccessfully treated with persistent immune depression. Moreover, the immunologic response to HAART has caused a PCP form which is included in the immune restoration inflammatory syndrome (IRIS). As of late 2004, 75.5% of patients cared for at Dr. Lucio Córdova Infectious Diseases Hospital were receiving HAART. This study compares PCP clinical characteristics in patients under the effect of HAART (n: 6) with those without antiretroviral therapy (n: 12). Among those with HAART, 83.3% (5/6) were without immunologic responses and 16.7% with virologic response. The median CD4 counts were low in both groups: 20 cells/mm(3) without HAART and 51 cells/mm(3) with HAART. There were no differences in most of PCP characteristics, and no IRIS cases were observed. HAART-receiving group had less severe disease and lower frequency of both, complications and steroidal therapy prescription (P 0.023).