The Fas ligand (FasL) and its receptor Fas play a key role in the initiation of an apoptotic pathway. We describe the expression of Fas receptor and ligand pair antigens in surgical samples collected from a cohot of 89 patients compared with 89 squamous cell carcinomas (SCCs), 45 dysplasias and 42 normal mucosae of the esophagus. TUNEL method was performed in 89 SCCs. Evaluation of FasL on normal mucosae displayed a heterogeneous immunoreaction in a minority of specimens, whereas SCCs exhibited a more extended and homogeneous reactivity. Fas-positive carcinoma cells revealed frequent apoptosis. Furthermore, a significantly longer disease-free survival can be observed in patients with Fas-positive tumors than in Fas-negative carcinomas and in patients with FasL-negative tumors than in FasL-positive carcinomas. In conclusion, FasL expression may play an important role in tumor progression. On the other hand, Fas-expressing carcinoma cells were associated with frequent apoptosis. Both FasL and Fas expressions correlate with prognostic significance in esophageal SCCs.