Over an eight year period, 1975 to 1982, 1,843 nosocomial bloodstream infections were identified by routine prospective surveillance at the University of Virginia Hospital (106/10,000 admissions). Despite a decline in overall bloodstream infection rates during the study period (P = .085), bloodstream infections due to gram positive organisms increased from 29 (1975-1978) to 43/10,000 (1979-1982), (P less than 0.001). Notably, rates for coagulase negative staphylococci increased from 5.2 (1975-1978) to 12.4/10,000 (1979-1982), (P less than 0.001). In 1982, coagulase negative staphylococci accounted for 17% of all bloodstream infections and were the most frequently isolated pathogens. Sixty-four percent of patients with coagulase negative staphylococci were in critical care units versus 41% with other bloodstream infections (P less than .05). The recognition of coagulase negative staphylococci as significant bloodstream pathogens markedly alters the clinician's approach to nosocomial septicemia.