The authors studied 69 squamous carcinomas of the middle or lower esophagus to evaluate prognostic factors. Clinical and histologic parameters that were evaluated included weight loss, esophageal obstruction at presentation, site, gross configuration, degree of tumor differentiation, vascular invasion, the status of resection margins, and stage. Blood group antigen (BGA) expression in the tumors was determined immunohistochemically and compared with blood type and antigen reactivity in adjacent normal mucosa. A loss of BGA expression was seen in 27 tumors. This finding was correlated with high stage but was not significantly linked to survival. DNA ploidy was determined by flow cytometry of paraffin-embedded tissues. Forty-one of 52 tumors were aneuploid, and 14 had two or more separate aneuploid populations. However, survival was not correlated with ploidy status. The degree of differentiation and stage of the tumors were the only two independently significant prognostic indicators in this study.