The significance of ultrasonography was tested in evaluation of cancerous invasion into the pleura and chest wall in patients with lung cancer. The degree of the invasion was ultrasonographically classified into four grades, that is, uP-0, uP-1, uP-2 and uP-3, corresponding with the classification proposed by the Japan Lung Cancer Society, which is graded by surgical findings. The total accuracy of this method was 77 percent. Especially for uP-3, which is the most critical grade regarding decisions on surgical intervention, this figure was 100 percent. It is suggested that this approach can delineate cancerous invasion into the pleura and chest wall sufficiently well for daily clinical use and staging of patients with lung cancer.