This study was aimed to assess the frequency, risk factors and etiology of bacteremia and antimicrobial susceptibilities of strains isolated from adult bacteremic patients hospitalized in Kocaeli University Hospital, Turkey during a 12-month period. Blood specimens obtained from a total of 2602 patients after at least 48 hours of hospitalization, were cultured in aerobic BACTEC 9120 and BACTEC 9050 (Becton-Dickinson, USA) automatized systems, and the identification and antibiotic susceptibilities of bacteria were performed by VITEK 1 (bioMerieux, France) system. Blood cultures of a total of 385 (14.7%) patients yielded bacterial growth; the contamination rate being 9.1% (238/2602) and nosocomial bacteria rate being 5.6% (147/2602). The distribution of the 147 (81 female, 67 male) bacteremic patients were as follows: 45% internal ward, 28% surgical ward and 27% intensive care unit. A total of 148 patients (81 female, 67 male) with no growth in their blood cultures were randomly chosen as the control group. The pathogens isolated from nosocomial bacteremias revealed 101 gram-positive bacteria (68.7%), 39 gram- negative bacilli (26.5%) and seven Candida species (4.7%). The most frequent gram-positive bacteria were staphylococci 84/101; 83.1%) and gram-negative bacteria were E.coli (14/39; 35.8%). Coagulase negative staphylococci (CNS) were isolated from 79% of the cultures evaluated as contaminants. Methicillin resistance was determined in 61.6% of S.aureus and 68.1% of CNS. Extended spectrum beta-lactamases were detected in 64% of E.coli, 62% of Pseudomonas spp., 47% of Klebsiella spp. and 24% of Acinetobacter spp. and resistance rates to ceftazidime and beta-lactam/beta-lactamase inhibitor combinations in these strains were 39-67%. The most effective drug group was found to be carbapenems with 3-26% resistance rates. The evalution of risk factors between patient and control groups revealed that mechanical ventilation (p < 0.05) and interventional catheters (except for intravenous catheters) (p < 0.05) were the most frequent sources of bacteremias.The most frequent focus of infection were the lungs (29.9%), followed by abdominal and catheter originated infections (23.8% each). The high rate of antibiotic resistance determined in the nosocomial bacterial isolates in our hospital indicated that antibiotic use policies in our setting should be taken under control. The high rate of contamination in blood cultures emphasize that more attention should paid for continous education about collection of blood culture specimens.