We have endeavoured to determine whether there is any difference in the bacteriological pattern of UTI and the antibiotic sensitivity patterns of the pathogens concerned between diabetic and non-diabetic patients. Over a period of 1 year, a total of 287 diabetic patients (221 females and 66 males) with community-acquired and nosocomial urinary tract infections were studied. There were 265 patients (228 females and 37 males) without any predisposition to urinary tract infections (UTI) and who served as controls. Although Escherichia coli was the predominant organism in community-acquired UTI in diabetic patients, it was found significantly less than in the non-diabetic population (P less than 0.005). The percentage of Klebsiella species causing community-acquired UTI in diabetic patients was significantly higher than in non-diabetics (P less than 0.005). The antibiotic sensitivity patterns of the organisms in the two groups, however, were not significantly different. The organisms isolated from nosocomial UTI in diabetics showed a significantly greater preponderance of Klebsiella spp. and a significantly lower percentage of E. coli when compared to community-acquired UTI in diabetics (P less than 0.005). Klebsiella spp. in nosocomial UTI of diabetics showed an overall increase in resistance to antibiotics. At least a quarter of the isolates of Klebsiella spp. in nosocomial UTI were resistant to third-generation cephalosporins. Patients with diabetes mellitus appear to have an increased incidence of Klebsiella spp. as the pathogen in both community-acquired and nosocomial UTI. Antibiotic resistance in the organisms isolated from nosocomial UTI is greater than that related to community-acquired UTI in diabetic patients.