A prospective randomized study to establish nosocomial infection (NI) rate was conducted at the Infectious Diseases Hospital (IDH) of Jakarta for 1 year in 1982/1983. Specimens were obtained from randomized patients for blood culture, rectal swabs and urine culture on day-1, 3 and 7. In addition, if there is any indication, other examinations were performed for patients hospitalized longer than 2 days, including culture of infusion needle. From 2,288 patients hospitalized during study period, 723 patients (aged 2 months-70 years) fulfilled the criteria for inclusion into the study, and NI was found in 191 (26.4%) patients with 285 infections according to the anatomical location. From 285 infections, highest infection rate was urinary tract nosocomial infection (15.9%), followed by nosocomial bacteremia (10,8%), lower respiratory tract infection (4.7%), gastrointestinal tract nosocomial infection (2.6%), skin nosocomial infection (2,4%), oral mucous membrane nosocomial infection (1,4%), nosocomial infection of infusion needle and the lowest rate was upper respiratory tract nosocomial infection (0.6%). The incidence was higher in female patients (29.1%) compared to male patients (24.0%). It was also higher in younger age group with highest in less than 1 year old (47.1%) and decreased as age of patients increased. Comparing the group of patients due to type of their illnesses, the incidence was significantly higher in febrile patients (52.0%) compared to diarrhea patients (12.9%) (p<0.05). It was also higher in group with community acquired infection (27.4°7o vs. 24.2%; in patients who received invasive procedures I intravenous fluid administration (30.6% vs. 19.6%; p<0,05), with catheterization (64.7% vs. 12.3%; p<0,01), received oxygen treatment (23.4 vs 3.4%, p< 0.001), received antibiotics prior to hospitalization (34.4% vs. 20.9%, p< 0.001), and for patients who were hospitalized for >7 days compared to <7 days (20.2% vs. 18.4%). Most common etiologic agents were gram negative organism (94.4%) with E.coli (20.3%) the most frequent, with gram positive organism was found in 5.6%. Some organisms recovered i.e. Klebsiella sp, Proteus sp, Alkaligenes sp and Citrobacter sp showed high resistency toward commonly utilized antibiotics in the hospital, i.e., Ampicillin, Tetracycline, and Chloramphenicol. Average duration of hospitalization for patients with NI (8.3 days) was longer than patients without it (4.3%). Fourteen out of 191 patients with NI died (7.3%), compared 0% in patients without NI, it was also significantly higher (p<0,001) in patients who received invasive treatment, oxygen (through mask/nasal cannule), mucus suction (45,5%) compared to who didn't get invasive treatment (4,3%). Mortality of NI patients was due to more severely of underlying disease of the NI patients.