Metabolism of antipyrine was studied in 12 patients with gastric carcinoma and 5 control subjects with peptic ulcer matched for sex, body weight, height, and smoking history. The mean antipyrine half-life was significantly longer (21.5 +/- 1.5 hr) in 3 patients with disseminated gastric carcinoma compared to control subjects (9.3 +/- 1.5 hr) (P less than 0.001). There was no significant difference in the mean antipyrine half-life between 9 patients with localized gastric carcinoma and control subjects. Similarily, the mean metabolic clearance rate of antipyrine was significantly lower (22.8 +/- 5.0 ml/hr/kg) in patients with disseminated gastric carcinoma compared to control subjects (52.6 +/- 13.4 ml/hr/kg) (P less than 0.02). Thus, the presence of gastric carcinoma in humans might alter antipyrine elimination. Significant negative correlation was observed between antipyrine half-life and albumin concentration (r = -0.786, P less than 0.01). These observations indicate that the decrease in antipyrine half-life is not primarily due to the presence of tumor but rather to the nutritional status of an individual.