In this trial, we examined the role of 4-g 5-aminosalicylic acid (5-ASA) enema in the long-term management of patients with previously refractory distal ulcerative colitis. Of 20 such patients treated with nightly 5-ASA enemas, 16 improved symptomatically, with 15 achieving clinical remission and 14 achieving sigmoidoscopic remission within 3 to 5 wk. An attempt was made to maintain clinical remission with 5-ASA enemas in these 16 by successively decreasing the frequency of administration to every other night and then every third night, as long as remission was maintained. Relapses were treated by reinstituting nightly 5-ASA enema administration followed by another attempt at tapering the frequency of administration. Follow-up has ranged from 5 to 16 months. Nine patients were rapidly tapered to every third night administration, but six relapsed. Of these six, four were brought into remission with reinitiation of nightly enemas and tapered to every three nights, whereas one ultimately required enemas every two nights for control and one required enemas nightly (with mild symptoms). Six other patients relapsed when the enemas were tapered to every two nights, and after retreatment on a nightly regimen, four could be maintained on an every third night regimen while two have required every second night administration. One patient has required nightly administration from the outset. Currently, one patient is off all medication, while eight are on an every third night, three are on an every second night, and three are on a nightly schedule. We conclude that in patients with distal ulcerative colitis refractory to conventional therapy but responsive to 5-ASA enemas, relapse is common as the frequency of 5-ASA enema administration is decreased, although some patients may be maintained on a less than nightly schedule. The optimal maintenance regimen remains to be determined.