Primary small cell carcinoma of the esophagus is a rare tumour. A primary composite tumour of the esophagus is even rarer and only four cases had been reported in the literature up to August 1998. The definitive histogenesis of this tumour remains controversial in spite of the additional information provided by electron microscopy and immunohistochemistry. In the presented case, histologically, the tumour tissue was composed of two malignant components: approximately 50% of a moderately differentiated squamous cell carcinoma, and approximately 50% of a small cell carcinoma. A lot of morphological transition zones were observed between the squamous cell carcinoma components and the small cell carcinoma components in some areas in the squamous cell carcinoma component. Histochemically and immunohistochemically, the small cell carcinoma cells demonstrated argyrophil granules, and Cytokeratin and Chromogranin A reactivity, but the squamous cell carcinoma cells demonstrated only Cytokeratin reactivity. Negative reactivity for argentaffin granules, neuron-specific enolase and S-100 were observed in both the small cell carcinoma and the squamous cell carcinoma components. Histological, histochemical and immunohistochemical findings suggest that a primary composite tumour of the esophagus may be derived from a totipotent primitive cell in the basal region of the squamous mucosa of the esophagus. The patient received chemotherapy preoperatively but died one month after the initial diagnosis.