Twenty-five bladder urine specimens from 13 patients with long-standing indwelling catheters were obtained by percutaneous suprapubic needle aspiration to avoid contamination by extraneous flora and cultured aerobically and anaerobically. Twenty different species of organism were isolated from twenty-four positive specimens. The isolates were predominantly gram-negative aerobic or facultatively anaerobic bacilli, with occasional gram-positive aerobic cocci and yeasts. One patient had Clostridium perfringens and a Bifidobacterium and another had Veillonella and two species of Bifidobacterium. Both patients had four concomitant aerobic or facultative bacteria present. Anaerobic bacteria may therefore be found in the bladder urine of some patients with indwelling urethral catheters, but their role in the initiation and perpetuation of urinary tract infection in this setting remains unclear.