We report a retrospective study of 39 homeless men hospitalized for acute pneumonia from April 1988 to March 1989. All of them had recently stayed in one of two shelters. A Streptococcus pneumoniae serotype 1, resistant to cotrimoxazole, was isolated in 29 patients (74 percent). Blood cultures were positive in 24 (61 percent). The patients were relatively young; none was over 70 years old. Thirty-five (90 percent) were heavy smokers; 32 (82 percent) were alcoholics. The radiologic pattern was atypical in 14 cases (36 percent). The only fatal case was linked to the adult respiratory distress syndrome. It is likely that the rate of outbreaks of pneumococcal pneumonia is underestimated. The homeless are at high risk for pneumococcal pneumonia. In addition, the closeness existing in shelters favors the occurrence of outbreaks. Consequently, we suggest that shelter residents would benefit from pneumococcal vaccination.