In 17 patients with anorectal fistulae the pelvis was examined by magnetic resonance imaging (MRI). The extent and the course of the fistulae and abscesses could be visualized by proton-density- and T2-weighted images. In 6 of 17 patients fistulae were seen that could not be detected by clinical investigation. In 2 cases additional pelvirectal abscesses were found. Most of the fistulae (5 of 6) had a complicated high suprasphincteric or rectovaginal course. It is concluded that with MRI anorectal fistulae and abscesses can be visualized and that this method is a worthful additional diagnostic tool in patients with complicated fistula-in-ano.