Fifty-five patients with oral submucosal fibrosis and an equal number of patients with no evidence of the disease were studied. All patients underwent upper gastrointestinal endoscopy and any abnormality was noted. Multiple oesophageal biopsies were obtained from the upper end of the oesophagus and from any endoscopically observed abnormality. The histological changes in the two groups were assessed blindly by an experienced histopathologist. Histological abnormalities were noted in the oesophageal mucosa in 2% of controls and 66% of patients with oral submucosal fibrosis (p < 0.0001). In the control group, acanthosis was seen in one patient, while in the patient group atrophy of the squamous epithelium was evident in 52%, hyperkeratosis in 52%, parakeratosis in 30%, dyskeratosis in 14%, acanthosis in 14%, and papillomatosis and mild dysplasia in 2% patients. Subepithelial collagenization was seen in 32 (64%) patients. The oesophageal abnormalities were seen more frequently in patients who had consumed Pan masala, Gutka, betel nut, tobacco or a combination of some or all of these, with or without betel leaf, for > or = 5 years compared to those consuming them for a shorter period of time (91% vs 46%, p < 0.001). It is concluded that oral submucosal fibrosis is not a disease confined to the oral cavity; the oesophagus may also be involved in about two-thirds of patients.