Abstract: This study detected the prevalence of Asymptomatic Bacteriuria (ABU) in residents of long term care facilities in Shiraz, Southwest Iran. From 100 residents aged between 55-95 years old, aseptically collected mid-stream urine samples underwent culture and antimicrobial sensitivity analysis. The prevalence rate of ABU was 53% with 95% CI 43.2 to 62.8% which was higher than that for elsewhere. ABU was observed more frequently in the females (57.7%), elderly (89%) and diabetic elderly subjects (72.3%). ABU in the diabetic elderly was also more than that for non-diabetic elderly subjects (p< 0.05). E. coli was the most common bacteria isolated. Resistance rate of gram positive bacteria to penicillin and cefazolin were 100% and those for tetracycline and vancomycin were 72.2 and 66.7%, respectively. The most gram negative bacteria were sensitive to aminoglycosides. Present results showed a higher prevalence of unknown ABU in the residents of nursing homes in Shiraz, Iran as compared to other countries in the world. It might be due to lack of efficient institutional care and uncontrolled diabetes mellitus or other factors influencing immunity.