Twenty specimens from patients who had undergone oesophagectomy for invasive squamous carcinoma of the oesophagus were examined for morphological evidence of human papillomavirus infection; it was found in 13 specimens. Nineteen specimens showed focal epithelial hyperplasia of the non-neoplastic mucosa. The material was also submitted to immunoperoxidase and modified Feulgen staining to detect viral antigen. Positive Feulgen staining was detected in the superficial layers of the squamous mucosa in 15 specimens, while immunoperoxidase was entirely negative. This demonstrates a possible association between human papillomavirus and oesophageal carcinoma and that the modified Feulgen method may be more sensitive than immunoperoxidase for the detection of viral antigen. Electron microscopy and molecular hybridisation would have to be used for confirmation.