Animal models of luminal cancers are important to understand and assess chemopreventive and chemotherapeutic interventions. However, the ability to assess tumor growth and response without animal sacrifice is limited. We assessed the ability of luminal sonography to assess the presence of tumor and its size in a surgical esophagojejunostomy model of esophageal cancer. Luminal sonography had a sensitivity of 88%, specificity of 100%, and accuracy of 93% in identifying the esophageal cancers. The tumor dimensions on luminal sonography were within 11% of autopsy measurements. Minimal tumor dimension was 2 mm and maximum 6.2 mm. The procedure was feasible without technical difficulty. In conclusion, rodent endosonography is a useful technique that can accurately determine the presence of tumors as well as their dimensions.