Most urinary tract infections begin as a cystitis secondary to decreased host resistance brought on by disruption of tissue integrity or a decrease in blood supply to the bladder. In the female, infrequent voiding and the uninhibited bladder are the most common causes of urinary tract infection and are best treated by healthy voiding regimens; while in the male, structural and functional obstructive uropathy are most often associated with urinary tract infection and are alleviated by lowering the high intravesical pressures via surgical or medical measures. The concept that host resistance is the determinant of infection rather than the organism has permitted the use of clean, intermittent self-catheterization; clean intermittent self-dilatation; and transurethral diverticulectomy in the therapy of a host of urologic disease syndromes.