Eighty-eight consecutive patients who underwent curative resection for colorectal cancer between 1983 and 1985 were studied prospectively to evaluate the roles of sequential CEA, TPA and CA 19-9 determinations and independent clinical examination in the early diagnosis of resectable recurrences. Twenty nine recurrences were detected between 8 and 38 months after primary surgery. CEA, TPA and CA 19-9 showed a sensitivity of 72%, 62% and 38%, and a specificity of 78%, 86% and 97%, respectively. Of eight recurrences in which CEA was not raised, five induced a rise in TPA and two a rise in CA 19-9. The rise in the serum concentration of one of the three markers was the first sign of relapse in 23 (79%) patients. Two second-look laparotomies based solely on a rise in serum markers were performed. In one case diffuse recurrent disease was found, and in the other a resectable solitary hepatic metastasis was found.