Infection, particularly pneumonia, is a major cause of morbidity and mortality in patients with systemic lupus erythematosus (SLE). This study was performed to assess the prevalence, causative organisms, and outcomes of community-acquired pneumonia (CAP) in Thai SLE patients, and determine the predicting factors for death. A retrospective chart review of adult SLE patients, age >16 years, seen at the Division of Rheumatology, Chiang Mai University over an 18 year period was carried out. Cases diagnosed with CAP were selected for this study. Of 542 SLE patients, a total of 56 episodes of CAP occurred in 52 patients. Their mean age +/- SD and duration of SLE were 37.98 +/- 11.48 years and 34.99 +/- 54.53 months, respectively. Thirty-three CAP cases (58.9%) occurred within the first year of diagnosis with SLE. The causative organisms identifiable in 40 patients (71.5%) were Mycobacterium tuberculosis in 12, Nocardia spp in 6, Aspergillus spp in 5, Staphylococcus aureus in 3, Pneumocystis carinii, Haemophilus influenzae, Escherichia coli, and Pseudomonas aeruginosa in 2 each, and Acinetobactor baumanii, Burkholderia pseudomallei, and Strongyloides stercoralis in 1 each. The remaining 3 patients had mixed bacterial infection. The overall mortality rate was 26.8%. Use of high dose prednisolone (> or =15 mg/day), and ventilator support were significantly associated with death.