A controlled trial has been carried out in order to compare the efficacy of enemas containing a high dosage of 5-ASA (4 g) versus enemas containing hydrocortisone 100 mg. The trial was conducted on 86 patients, 44 of whom received 5-ASA and 42 received hydrocortisone. The results were favorable in terms of clinical, sigmoidoscopic, and histologic criteria for 5-ASA treatment. Other aspects have been investigated, such as retrograde spread of enemas which have been shown to reach the left colon. No nephrotoxicity was detected. The long term experience confirmed the preliminary positive results.