Posterior abdominal rectopexy was performed in 12 patients with a full-thickness rectal prolapse: 9 had faecal incontinence. The prolapse was successfully controlled in all cases and six of nine patients were rendered continent. Physiological studies in patients were compared with age- and sex-matched controls. Preoperative anal pressures were significantly lower than in controls at rest (R), during maximum pelvic floor contraction (Sq) and attempted defaecation (St) (R, P less than 0.005; Sq, P less than 0.005; St, P less than 0.005). Anorectal angles were significantly more obtuse in patients than in controls (R, P less than 0.05; St, P less than 0.025). None of these parameters changed significantly after abdominal rectopexy. Median rectal emptying significantly decreased after operation (preoperative 83 per cent/min; postoperative, 58 per cent/min, P less than 0.05). Median perineal descent during attempted defaecation also significantly decreased after operation (preoperative, 8.5 cm; postoperative, 7.1 cm; P less than 0.025). Parameters which predicted return of continence included: delayed leakage during the saline infusion test (P less than 0.025), a narrow anorectal angle during pelvic floor contraction (P less than 0.025), minimal pelvic floor descent during contraction (P less than 0.05), and a long anal canal at rest (P less than 0.05) and during pelvic floor contraction (P less than 0.025).