Clinicopathologic data on 201 patients who underwent surgical resection of esophageal squamous cell carcinoma, with or without intramural metastasis (IM), were analyzed to determine the significance of IM for patient prognosis and survival. In 24 (11.9%) patients IM was observed. There was one (1.4%) in 74 cases in Stage 0, I, or II, and 23 (18.1%) in 127 cases in Stage III or IV, based on the new pTNM classification. There was a statistically significant Cox-Mantel test difference in the percentage survival curves of the patients, both in all stages (P less than 0.01) and in only Stages III and IV (P less than 0.05), as a function of the presence or absence of IM. Lymph node metastasis and distant organ metastasis were observed in 22 (91.7%) and seven (29.2%) of the 24 patients, respectively, with IM and in 111 (62.7%) and 13 (7.3%) of the 177 patients without IM. For both types of metastasis, the incidence was significantly lower in the patients without IM (P less than 0.01). Seventy percent of IM on the proximal side was detected during preoperative clinical examination. These data indicate that the presence of IM is an important factor for preoperative and postoperative evaluation of the prognosis of patients with esophageal squamous cell carcinoma.