Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) selectively induces apoptosis in cancer cells and may be involved in protection from metastases. TRAIL receptor (TRAIL-R) 1 and TRAIL-R2, but not TRAIL-R3 and TRAIL-R4, mediate apoptosis. We examined the expression of TRAIL and its receptors in normal and neoplastic colon epithelium, and studied its correlation with prognosis in colon cancer. Immunohistochemistry was performed on normal colon mucosa (n = 10), colon adenomas (n = 20), and R0-resected Unio Internationale Contra Cancrum stage II/III colon carcinomas (n = 129). Disease-free survival was examined by Kaplan-Meier estimates and the log-rank test. Prognostic factors were determined by multivariate Cox-analysis. In normal colon mucosa, TRAIL and TRAIL-R2 were expressed mostly in the surface epithelium, whereas TRAIL-R1 and TRAIL-R4 were detected all along the crypt axis. In adenomas, this expression pattern was mostly retained, although some adenomas also neoexpressed TRAIL-R3. In carcinomas, the expression of TRAIL and TRAIL receptors was much more variable. TRAIL, TRAIL-R2, TRAIL-R3, and TRAIL-R4 expression did not correlate statistically with disease-free survival (multivariate analysis: P = 0.54, P = 0.67, P = 0.45, and P = 0.69, respectively), but TRAIL-R1 expression was significantly associated with disease-free survival in colon cancer (multivariate analysis: P = 0.003). TRAIL-R1 is an independent prognostic factor in R0-resected Unio Internationale Contra Cancrum stage II/III colon cancer.