We studied all patients with community-acquired pneumonia who were admitted to our 800-bed adult acute care hospital from 1 November 1981 to 15 March 1987. The 719 patients had a mean age of 63.2 years; 18% were admitted from nursing homes, and 18% required ventilatory assistance as part of the therapy for pneumonia. Patients with nursing home-acquired pneumonia were significantly older; had a higher mortality (40% vs. 17%); were more likely to be admitted in January; were less likely to complain of cough, fever, anorexia, chills, headache, nausea, sore throat, myalgia, or arthralgia; and were more likely to be confused than those admitted from the community. Pneumonia of unknown etiology and aspiration pneumonia were more common and Mycoplasma pneumoniae infection less common among those with nursing home-acquired pneumonia. Streptococcus pneumoniae accounted for 58% of the 48 cases of bacteremia. None of the bacteremic patients received antibiotics before admission, compared with 34% of the nonbacteremic patients. Aerobic gram-negative rod bacteremia was not more frequent among nursing home patients than among those from the community. The overall mortality was 21% (8.5% for those less than 60 years of age and 28.6% for those greater than 60 years old). By multivariate analysis the following variables were significant predictors of mortality: number of lobes involved by the pneumonic process, number of antibiotics used to treat the pneumonia, age, admission from a nursing home, ventilatory support, and the number of complications that occurred while the patient was in the hospital.