A complicated UTI (cUTI) is an infection associated with a condition, such as structural or functional abnormalities of the genitourinary tract or the presence of an underlying disease, which increases the risks of acquiring an infection or of failing therapy. To study the prescribing pattern in cUTI in a tertiary care hospital along with the antimicrobial sensitivity of the causative organisms. This prospective observational study was conducted in Institute of Nephro-urology, Bangalore from January to December 2010. The details of demographics, past medical history, details of the drugs including dose, duration of therapy, route of administration, urine culture and antimicrobial sensitivity were obtained from the case records of the patients. The prescriptions were analysed for the WHO/INRUD indicators. Descriptive statistics was used for the analyses of the results. Mean ± Standard deviation, percentages was used wherever appropriate. A total of 84 patients were included in the study, of which 49 were males and 35 were females. The age of the patients ranged from 16 to 82years, with an average of 48.4years. Mean duration of antimicrobial agents (AMAs) therapy was 11.23±6.1days. Only 34.5% of the patients had Culture and sensitivity of urine done, of which E.coli was detected in about half of them. E.coli was sensitive to Piperacillin & Tazobactum, followed by Cefoperazone & Sulbactum. Most commonly used AMAs include Cephalosporins (29%), Quinolones (26%) and Penicillins (23%). Many patients with cUTI were associated with Type 2 Diabetes mellitus. Average number of drugs per prescription was 6.21 ± 3.36 with number of antibiotics per prescription was 2.1 ±0.78 and number of injections per prescription was 1.9±1.37. The prescription of empirical AMAs were in accordance with EUA guidelines. But, the use of large number of AMAs prescribed after discharge needs to be reduced. The shift from broad spectrum to narrow spectrum AMAs based on laboratory results needs to be improved in our hospital. Tendency towards polypharmacy and intravenous AMAs also should be reduced in our hospital. There is an urgent need for implementing region specific antimicrobial guidelines for the treatment of cUTI.