Delayed hypersensitivity skin responses to costus root oil were measured in patients with colon, stomach, breast and lung cancer and in healthy controls. Cancer patients were staged according to tumor spread. Differences were demonstrated between cancer patients and controls. Patients with localized cancer showed no impairment, but diminished responses did occur in patients with advanced or metastatic cancer. There were no significant differences among any cancer groups with lymph node involvement. In the late cancer stage, costus root oil sensitivity was lost to a greater extent in patients with gastric cancer than in those with colon cancer.