Abstract: Prospective studies among 591 patients, admitted into 4 departments of our hospital March 1st, through May 31sr, 1988, were carried out. We estimated that 16.2 of NI occurred among every 100 admissions. The rate of NI in the respira tofy tract was highest, and followed by NI of urinary tract. biliary tract and surgical wound etc.72.9% of organisms involved in NI were Gram-negative bacilli （GNB）. Ps. aeruginosa, E. coli, E. cloacae and Klebsiella spp etc were more identified. Gram-positive cocci were found in 12.9%. Candida spp was present in 14.1%.The bacterial resistance in NI was more than in communityacquired infections （CI）. The frequency of resistance （FR） to ampicillin, carbenicillin, gentamycin and tobramycin of GNB in NI were higher than 45.0%. The FR of S. epidemieis in NI to 8 semisynthetic penicillins, erythromycin, SXT and vancomycin were up to 60%. 5 strains of MRSA were identified in NI. It is suggested that rational administration of antibiotics should be carefully noted.