The influence of socioeconomic status on the features and evolution of community-acquired pneumonia in 107 consecutive hospitalized patients was investigated. Thirty-four (31.8%) patients were considered to have a low socioeconomic status. These patients were more likely immigrants, middle-aged, with fewer comorbid illnesses, and were more often tobacco, alcohol, or drug consumers (P<0.01). The distribution of etiologies was significantly different according to socioeconomic status, with tuberculosis occurring more frequently in the low socioeconomic group (P < 0.05). Low socioeconomic status was not associated with a more severe presentation or outcome of pneumonia but was an independent factor that predicted a significantly longer length of hospitalization (5.9 days longer; 95% confidence interval, 2.2-9.5 days; P<0.003), entailing a substantial excess cost per hospital stay.