We documented the natural history of esophageal carcinoma and its rapid growth by measuring the change in tumor diameter radiographically in 10 patients during an observation period because the diagnosis had been missed. Nine men and one woman (age range, 48-74 years; mean, 60 years) were included in the study. Eight patients had undergone esophagography for gastrointestinal complaints and had lesions missed on the initial interpretation that were apparent on retrospective review after the patient had returned with more severe complaints and undergone repeat studies; two patients had refused treatment. The tumor was squamous-cell carcinoma in all. The treatment-free retrospective observation period ranged from 4 to 19 months (mean, 12.2 months) and was shorter for elevated (mean, 9.2 months) than for depressed lesions (mean, 16.8 months). The longitudinal diameter increased from 10-100 mm initially (mean, 30.5 mm) to 32-150 mm (mean, 74.9 mm). No correlation existed between the increase in size and histologic features. This documentation of the rapid increase in the size of esophageal carcinoma involving at least the submucosa confirms clinical impressions of the aggressive nature of this lesion and offers an explanation of why this disease is seldom detected at an early stage and long-term survival is so poor after the early stage of disease.