With the proposed introduction of a flexible sigmoidoscopic screening programme for colorectal cancer, patient compliance is of paramount importance. Therefore, the bowel preparation providing optimum cleansing of the bowel with the least associated discomfort and inconvenience for the patient must be found. Patients were randomized to receive either Picolax the evening before the examination or self-administered Fleet enemas prior to the investigation. The endoscopist and nurse practitioner who collected data on a standard questionnaire were blinded to the preparation used. Bowel preparation was graded by the endoscopist as: excellent, good, adequate or poor. One hundred and two consecutive patients were randomized: 56 to the Fleet enema group and 46 to the Picolax group. Self-administered Fleet enemas provided a significantly superior bowel preparation with 52 (93%) being judged adequate or better, as opposed to 34 (74%) in the Picolax group. In addition, Fleet enemas were associated with significantly fewer adverse associated symptoms: 11 (20%) vs 24 (52%). Patients reported to be willing to receive Fleet enemas again in 53 (95%) vs 37 (80%) for the Picolax group. The self-administered Fleet enema is superior to Picolax in terms of bowel preparation for flexible sigmoidoscopy and the incidence of associated adverse symptoms.