We reviewed the courses of 63 patients with inflammatory bowel disease (IBD) treated in a private gastroenterology practice. All were allergic, unresponsive, or in some way intolerant of sulfasalazine and therefore were treated with Eudragit-S—coated mesalamine (Asacol). Thirty-eight patients had ulcerative colitis (UC) and 25 had Crohn's disease. In 22 and 14, respectively, mesalamine was used to treat active disease; in 16 and 11, respectively, it was introduced to maintain remission. In some patients, mesalamine was used along with other medications. Symptomatic and endoscopic response was seen in seven of nine (77%) with active UC treated with mesalamine alone; remission was maintained in seven of eight (94%) when mesalamine was used alone. Therapeutic success was noted in eight of 10 (80%) with active Crohn's disease, and remission was maintained in seven of nine (78%) when mesalamine was used alone. Adverse reactions of varying severity occurred in 21 of 63 (33%), but the drug had to be terminated in only 9 of 63 (14%). Eudragit-S—coated mesalamine appears to be effective in the treatment and maintenance of remission of UC in 82% of those patients allergic or intolerant to the parent drug, sulfasalazine. Furthermore, contrary to what was expected, we found it effective in a much larger percentage of patients with Crohn's disease (79%) than the parent drug.