Objectives: The main objective of this study was to investigate the bacterial infections of urinary tract in patients with urolithiasis. The patients were referred to and/or visiting the Urology Department in Tikrit Teaching Hospital in Tikrit city. Methods: The present study was carried out from November 2011 until July 2012. One hundred and sixty patients with urolithiasis were included in the present study whose ages ranged from 12 to 70 years. Male to female ratio was almost 2:1. The control group consisted of two groups;group one consisted of 40 persons (20 males and 20 females) who were selected randomly from Tikrit city during the period of this study and they had no previous personal nor family history of urolithiasis, while group two consist of 40 persons (20 males and 20 females) infected with urinary tract infection. Urine culture was done for all the patients and the control group. Results: Forty five percent (45/160) of these had UTI’s. Six patients revealed mixed bacterial growth. Eighty-four percent (38/45) of patients with UTI were infected with gram negative organisms where as only 16% (7/45) of patients were infected with gram positive organisms. The majority of the gram negative bacteria isolated belonged to the family Enterobacteriaceae particularly E. coli as it was isolated from 14 (31%) cases. The urease producing bacteria were isolated from 31 cases (50%). Conclusions: UTI’s in urolithiasis was more frequent in females than males and the percentages were 28/45 and 17/45 respectively. The most effective antimicrobial agent was amikacin and the least effective one was ampicillin, whereas ciprofloxacin, cefoxitin, levofloxacin, nitrofurantoin, nalidixic acid, chloramphenicol, amoxycillin and gentamicin were effective at different levels.