To determine the aetiological agents of pulmonary infections in HIV-infected Tanzanians and to correlate the causative agents with clinical, radiographic features, and mortality. DESIGN: A prospective study. SETTING: Kilimanjaro Christian Medical Centre (KCMC), Tanzania. SUBJECTS: Bronchoalveolar lavage fluid (BAL) were obtained from 120 HIV infected patients with pulmonary infections. BAL for causative agents was analysed and correlated with clinical and radiographic features, and one-month outcome. RESULTS: Causative agents were identified in 71 (59.2%) patients and in 16 of these patients, multiple agents were found. Common bacteria were identified in 35 (29.2%) patients, Mycobacterium tuberculosis in 28 (23.3%), Human Herpes Virus 8 (HHV8) in 12 (10%), Pneumocystis jiroveci in nine (7.5%) and fungi in five (4.2%) patients. Median CD4 T cell count of the patients with identified causes was 47 cells/microl (IQR 14-91) and in the 49 patients with undetermined aetiology was 100 cells/ microl (IQR 36-188; p = 0.01). Micronodular chest radiographic lesions were associated with presence of M. tuberculosis (p = 0.002). The one-month mortality was 20 (16.7%). The highest mortality was associated with HHV8 (41.7%) and M. tuberculosis (32.1%). Mortality in patients with undetermined aetiology was 11.3%. No death occurred in patients with PCP. CONCLUSION: In this population of severely immunosuppressed HIV-infected patients with pulmonary infection a variety of causative agents was identified. Micronodular radiographic lesions were indicative of TB. High mortality was associated with M. tuberculosis or HHV8. No death occurred in patients with P. jiroveci infection