Bacterial UTIs are a common problem in patients with diabetes mellitus. Bacteriuria is more common in diabetic women than in non-diabetics owing to a combination of host and local risk factors. Upper tract disease is also more common in this group. Diabetics are at higher risk for intrarenal abscess, with a spectrum of disease ranging from acute focal bacterial pyelonephritis to renal corticomedullary abscess to the renal carbuncle. A number of uncommon complicated UTIs, such as emphysematous pyelonephritis and emphysematous pyelitis, occur more frequently in diabetics. Because of the frequency and severity of UTI in diabetics, prompt diagnosis and early therapy is warranted.