Aims and background: The increased level of blood glutathione (GSH) is an important biochemical feature in animal epithelial tumor. The aim of this study was to investigate the blood GSH concentrations in well characterized cancer patients and healthy volunteers. Methods: Two different groups of carcinoma cases were used. The first group consisted of 15 blood samples drawn from disseminated gastric adenocarcinoma patients, and the second group comprised 15 samples obtained from localized or locally advanced skin carcinoma cases without lymph node metastasis. GSH and hemoglobin concentrations were measured by using the method of Beutler et al. Results: The mean blood GSH in patients who had advanced malignant disease was 129.73 +/- 7.49 mg/dl and in patients who had localized cancer was 96.24 +/- 3.90 mg/dl. These results indicate that the blood GSH level is 31% higher in localized carcinoma cases and 78% higher in metastatic disease than those of controls. Blood GSH concentrations were expressed on the basis of blood volume and also on hemoglobin content. Similar results were calculated with either mode of expression. Conclusion: By comparing the two groups of patients, we found that higher blood GSH concentration was correlated with metastatic growth.