Total 3,808 blood specimens from 1,891 patients were cultured at Seoul National University Hospital in 1980. Laboratory data were analyzed and the following results were obtained. 1) Average number of specimens requested per one patient was 2. 2) 328 patients (17.4%) of the total 1,891 patients had at least 1 positive blood culture. Of these patients with bacteriologically established bacteremia, 6.7% had multiple isolates from a single specimen (poly-microbial bacteremia), and 2.1% had different isolates in additional blood culture (bacteremic superinfection). 3) Distribution of organisms (single isolate) involved in patients with bacteriologically proven bacteremia were gram-negative bacilli 71.3%, gram-positive cocci 27. 1% and anaerobes 1.6%. Frequently isolated organisms in decreasing order were Enterobacterieae (31%), Salmonella spp. (17.4%), Psendomonas spp. (10.5%), Staph. aureus (9.2%) and alpha hemolytic streptococcus(7.5%). 4) Salmonella typhi was susceptable to commonly used antimicrobial agents but many of the isolates of Staph. aureus, E. coli and Ps. aerugiuosa were resistant to routinely tested antimicrobial agents