Intensive care unit (ICU)-acquired infections can bring some degree of morbidity and mortality to patients staying in the ICU. In this study, over a 6-month period, the prevalence of infections and mortality rates among ICU patients, the predominant organisms and their resistance patterns were determined in a cross-sectional study. Samples of all the patients hospitalized longer than 48 h in two Shiraz university teaching hospitals in Shiraz, Iran, were microbiologically cultured, and antimicrobial susceptibility was determined using the disk diffusion method. We studied 123 specimens from 89 patients aged 1 month to 80 years (38.3-/+13.4), and among them 46 patients (51.7%; 95% CI, 41.3-62.1%) showed infection based on culture and clinical findings. Of these, 37 patients (41.6%) had more than one ICU-related nosocomial infection and 9 patients (10.1%) had only one ICU-related nosocomial infection. The overall mortality rate for ICU-acquired infections was 10.9% (5 patients). Gram-negative bacteria were significantly more involved in infections than were Gram-positive bacteria (P<0.05). The most frequently reported infections were urinary tract infections. The most frequently isolated bacteria were Pseudomonas (39.1%), which was mainly sensitive to amikacin and ceftazidime. Our study results underscore the importance of specific measures for infection control in critically ill patients in ICUs in Shiraz, Iran, especially when using urinary catheters.