The author conducted an analytic study on bacteriologic data from various infectious conditions which had been treated in Department of Orthopaedic Surgery, Guro Hospital, Korea University during the period from September, 1983 through December, 1989 to find out any changes, if ever, of organisms' prevalence and their sensitivity pattern against current antibiotic drugs. The results were as follows; 1. Positive culture of microorganisms were obtained in number of 354 from 293 cases out of total 916 cases which were all apparently of infectious conditions. 2. The diagnosis from which positive cultures obtained were osteomyelitis in 116 cases(39.8%), open fracture in 69 cases(23.6%), wound infections in 51 cases(17.7%), soft tissue infections in 38 cases(12.9%), pyogenic arthritis in 17 cases(5.4%) and mixed infection of bone and joint tuberculosis in 2 cases(0.7%) in order of frequency. 3. The identified organisms were 19 species and the coagulase positive and negative Staphylococcus continued to be the most frequent offender occupying 50.2% of the total, even though the percentage was a bit lower than those of previous reports. The second most frequent organism was Pseudomonas species to take 21.5% of the total. 4. The ratio between gram positive and negative organisms was 1.21:1 showing increasing tendency in prevalence of gram negative over positive organisms. 5. Stapylococcus species showed sensitivity to Cephalosporins by more than 85%(Cephalothin 86.0%, Cefotaxime 85.4%) while it showed resistance to Penicillin G by 87.9% and to Erythromycin by 82.7%. 6. Streptococcus species showed high sensitivity to Cephalosporins(Cephalothin 92.3%, Cefotaxime 92.3% ) and its resistance was generally low even to other drugs. 7. Pseudomonas species showed sensitivity to Aminoglycosides by more than 70% (Amikin 82.7%, Tobramycin 74.6%) while it showed resistance to Tetracyclin by 95.5% and to Ampicillin by 95.8%. 8. Stapylococcal and Streptococcal infections have decreased and opportunistic infections by gram negative organisms such as Pseudomonas species and Escherichia species have markedly increased over the previous reports in their prevalency.