Of 78,057 patients discharged from a community hospital from 1972 through 1976, nosocomial infections developed in 3.58 per cent. Nosocomial infections of all types were 13.2 times more frequent for patients with rapidly fatal underlying illness and 3.4 times more frequent for patients with ultimately fatal underlying illness than in cases of nonfatal underlying illness. Outbreaks of epidemics or clusters of infections caused by the same organism were distinctly uncommon. These outbreaks accounted for only 49 of the 2,798 nosocomial infections found. No distinct trends, either increases or decreases, of infection rates by pathogen, site of infection, or service were noted during the study period. Sensitivity of the common pathogens to antibiotics also remained stable.