Perioperative ultrasonography was performed in patients with gastric cancer to diagnose a presence of paraaortic lymph node metastasis, and its availability was examined. From the measurements of long and short diameters of the lymph node cross sections previously drawn, the diagnosis criterion for metastasis-positive was designated as that the long one was more than 7cm and the short-to-long diameter ratio, more than 0.5; or that the imaging modality revealed a low echogenic lesion or a mixture of irregular low and high echogenic lesions. As a result, it was found that perioperative ultrasonography offered usuful informations for diagnosis of para-aortic lymph node metastasis in gastric cancers with 100% in the sensitivity, 90% in specificity, and 93% in overall acurracy. It can be an adjuvant method for decision-making of surgical procedure.