During 1991 to 1993 12,064 blood cultures from patients with suspected bacteraemia were examined in a newly established Microbiology Department of the Brno-Bohunice Faculty Hospital. A total of 1,790 (14.8%) blood cultures were positive, 746 (6.2%) were contaminated. The incidence of positive blood cultures was 7.1/1,000 patients admitted in 1991, 10.0/1,000 in 1993. From the positive blood cultures 853 different microbes were isolated: 486 gram-negative bacteria (56.9%), 315 gram-positive ones (36.9%), 9 anaerobes (1.1%) and 44 yeasts (5.2%). In 69 cases (3.8%) more than one agent was recovered from one blood culture. The most frequently isolated microbes were gram-negative non-fermenting rods other than P. aeruginosa (15.7%), E. coli (12.1%), S. aureus (11.4%) and coagulase-negative staphylococci (10.1%). From direct inoculation of blood 22.6% blood cultures were positive, and another 55.3% positive after 1-day growth in broth. In 1993 there were 306 patients with positive blood cultures; in those blood for the culture was collected during the first 48 hours after admission: in 76 (32.7%) admitted to medical wards, in 7 (9.6%) to surgical wards. The mortality of patients with positive blood cultures was 23.5%.