Esophageal dysplasia and carcinoma were reviewed in the surgical specimens obtained from 37 patients with squamous cell carcinoma and 4 with adenocarcinoma; special attention was paid to the continuity of both lesions. Two hundred forty dysplasias and 113 carcinomas in situ (CIS) were recognized in the squamous cell carcinoma cases and 2 dysplasias and no CIS in the adenocarcinoma cases. The CIS often was accompanied continuously by severe dysplasia rather than mild or moderate dysplasia, suggesting some relationship between the CIS and the severity of dysplasia. However, many dysplastic lesions were located separately from the carcinoma. The frequency of appearance of the dysplasia near the CIS was low (11%), demonstrating a negative dysplasia-CIS sequence in many of the esophageal cancers. Lymphocytic infiltration was investigated further beneath the dysplasia or CIS. The degree of lymphocytic infiltration with lymphoid follicles correlated with the severity of dysplasia and was the highest in CIS.