Mortality and hospitalization rates for pneumonia have increased among older Americans during recent years (1979-86), despite a national commitment to the reduction of premature deaths from pneumonia. A prospective study of deaths and hospitalizations attributable to pneumonia was conducted among 5,474 subjects ages 55 and older who participated in the NHANES I Epidemiologic Followup Study. Prevalent chronic conditions, health behaviors, and nutritional status indicators, measured at baseline, were examined in relation to pneumonia hospitalization and death during 12 years of followup. Mortality and hospitalization rates for pneumonia were higher among men than women, and higher among those ages 65 and older than among those 55-64 of both sexes. Risk of pneumonia death was higher among subjects with a history of congestive heart failure, stroke, cancer, or diabetes. Risk of pneumonia hospitalization was higher among subjects with a history of chronic obstructive pulmonary disease and among men who were current smokers. Daily alcohol consumption did not increase risk of pneumonia in this study population. Four measures of nutritional status were examined taking age, prevalent chronic conditions, and cigarette smoking into account: body mass index, arm muscle area, and serum albumin and hemoglobin levels. Risk of pneumonia death was 2.6 times higher in men in the lowest quartile, compared with men in the highest quartile, of body mass index. Similarly, the risk was 4.5 times higher among men in the lowest quartile of arm muscle area. Risk of death from pneumonia was 3.6 times higher among women in the lowest quartile of serum albumin levels compared with women in the highest quartile. Relative risks for these nutritional status indicators remained elevated after adjusting for age and the medical history risk factors. These risk factors should be taken into account when designing and evaluating pneumonia vaccination trials and community prevention programs.