Objective: To determine the incidence of nosocomial infection by service and site and the distribution of pathogens involved during a five year period. Setting: Hospital - wide. Intensive Care Unit and Bunts Unit of Qatif Central Hospital. Subject: Patients with proven nosocomial infections. Methods: Analysis sis of patient's data collected by active surveillance using a combination of case finding methods. Results: The overall rate of nosocomial Infection was 2.2%. According to the hospital services the rates of nosocomial infection ranged from 0.8% to 28%. The highest rates were seen in the Burns Unit (28%) and Intensive Care Unit (24%); the major sites of nosocomial infections: were, urinary tract (29%), post operative wound infection (24%), respiratory tract infection (18.%) and blood-stream infection (11%). Pseudomonas spp. was the most frequently isolated nosocomial pathogen (18.9%), followed by S. aureus, (16.5%) Klebsiella spp. (13.5%), E coli (9%), Candida spp (5.5%), Coagulase negative staphylococci (5.3%) and Enterococci (5.5%). Nosocomial infection is a problem in Bums Units and in high dependency areas. In Saudi Arabia, like other countries. prospective active surveillance and dissemination of information to health care staff may identify areas where infection control prevention effort should be focused.