BACKGROUND--Collagenous colitis and lymphocytic colitis present with a similar clinical picture. Whether these conditions are separate entities or whether they represent different pathological stages of the same condition is an unresolved issue. PATIENT--This is a case of collagenous colitis following a fulminant course in which a colectomy was necessary. In the operative specimen the thickened collagen plate, which had been present only two weeks preoperatively had been lost and the pathology was of a lymphocytic colitis. Six months postoperatively this patient developed a CREST syndrome and primary biliary cirrhosis. CONCLUSIONS--This case shows the lability of the collagen plate and the common ground between collagenous and lymphocytic colitis, and presents evidence that these two conditions are different manifestations of the same disease. It also describes for the first time an association between collagenous colitis and CREST syndrome and primary biliary cirrhosis.