Although multiple studies have investigated community-onset urinary tract infections (UTI), population-based data are lacking. We therefore conducted population-based laboratory surveillance in order to define the incidence, demographic risk factors, etiology, and antimicrobial susceptibilities of community onset UTI in a large Canadian region. Laboratory surveillance for all community onset UTIs among residents of the Calgary Health Region (population ~1.2 million) was conducted during 2004/2005. Repeated positive samples within a 1-month period and those infections first cultured more than 2 days after admission to a hospital were excluded. A total of 40,618 episodes of community onset UTI occurred among 30,851 residents for an overall annual incidence of 17.5 per 1,000. Seventy-four percent of the cultures were submitted from ambulatory patients, 18% from hospitalized patients within the first 2 days of admission, and 9% from nursing home residents. Females were at significantly increased risk as compared to males (30.0 vs 5.0 per 1,000, RR 5.98; 95% CI, 5.8–6.15; p < 0.0001) as were the very young and very old. The most common infecting organisms were Escherichia coli (70%), Klebsiella pneumoniae (7%) and Enterococcus species (6%). Overall resistance rates among first isolates per patient tested were 14% for trimethoprim/sulfamethoxazole, 8% for cefazolin, 7% for nitrofurantoin, 6% for ciprofloxacin, 4% for gentamicin, and 2% for ceftriaxone although rates differed significantly based on sending location and patient age. This study provides novel information on the epidemiology of community-onset UTIs in a non-selected Canadian population. The occurrence, etiology, and resistance rates of community onset UTI differ significantly among definable population groups.