BACKGROUND Various injectable bulking agents have been used for the treatment of faecal incontinence (FI). However, encouraging early results are not maintained over time. This study aimed to assess short- and medium-term results of a new bulking agent for the treatment of FI. METHODS The Gatekeeper(™) prosthesis comprises a thin solid polyacrylonitrile cylinder that becomes thicker, shorter and softer within 24 h after implantation. Fourteen patients with FI underwent treatment with Gatekeeper(™) under local anaesthesia. Four prostheses were implanted in the intersphincteric space in each patient, under endoanal ultrasound guidance. Number of episodes of major FI, Cleveland Clinic FI score (CCFIS), Vaizey score, anorectal manometry, endoanal ultrasonography (EUS), health status and quality of life (Short Form 36 and Faecal Incontinence Quality of Life questionnaires) were assessed before and after treatment. RESULTS Mean(s.d.) follow-up was 33·5(12·4) months. There were no complications. There was a significant decrease in major FI episodes from 7·1(7·4) per week at baseline to 1·4(4·0), 1·0(3·2) and 0·4(0·6) per week respectively at 1-month, 3-month and last follow-up (P = 0·002). CCFIS improved significantly from 12·7(3·3) to 4·1(3·0), 3·9(2·6) and 5·1(3·0) respectively (P < 0·001), and Vaizey score from 15·4(3·3) to 7·1(3·9), 4·7(3·0) and 6·9(5·0) respectively (P = 0·010). Soiling and ability to postpone defaecation improved significantly, and patients reported significant improvement in health status and quality of life. At follow-up, manometric parameters had not changed and EUS did not demonstrate any prosthesis dislocation. CONCLUSIONS The Gatekeeper(™) anal implant seemed safe, reliable and effective. Initial clinical improvement was maintained over time, and follow-up data were encouraging.