Background & Objectives: Identifying urinary tract infection, especially in infants and young children is very important from the viewpoint of start of treatment, and if it is delayed probably the children are affected by risk of failure to thrive, sepsis and chronic problems such as renal scars, increase of arterial blood pressure and renal failure. Increasing usage of antibiotics, result in AB resistance microorganism. This study was done because of bacterial differences in resistance in different regions and the change in the rate of resistance in UTI.

 Methods:�This research is a descriptive-prospective study 510 children under the age of 12 as the study samples were chosen. These children were referred to clinics of Ardabil Aliasghar and Sabalan Hospitals in 2006. Their urine culture colony was above 100000. Data gathering was accomplished by their parents through questionnaire and interview's then gathered Data were analyzed by computer software programs of the SPSS and Excel.

 Results:�Findings of research showed that symptoms of malodorous urine (54.7%) in children under 12 months, dysuria (58.9%) in 1-3 years age groups, frequency (54.8%) in 3-6 years old groups dysuria (49.2%) in 6 years old groups and above were most prevalent symptoms which were reported. From the viewpoint of gender differences UTI in girls was 4 times more than that of boys that this difference in 1-3 years old groups was highest range (4.8 to 1). About antibiotical resistancy of microorganisms, Ampicillin with 78.9% resistance, Co-trimoxazole with 66%, Cephalexin with 62.8% and cephazoline with 33.3% were most resistant antibiotics respectively. E-coli resistance against gentamicine was 15.8%, that compared with other microorganisms is very high and its resistance against ceftriaxon was 8%, which is low compared with other microorganisms.

 Conclusion: Findings of research showed the variety of UTI symptoms in children and also showed that drug resistancy against Ampicillin, Co-trimoxazole, Cephalexin and cephazoline is high.