Although cortisol is a powerful modulator of the immune system and inhibits production of pro-inflammatory cytokines, adrenocorticotropic hormone (ACTH) levels do not correspond to the chronically elevated concentrations of cortisol in cancer patients. Thyroid stimulating hormone (TSH) has been shown to have an effect on immunological functions. Actually it is not known whether cortisol, TSH and IL-6 have an effect on tumor progression via modulation of cell mediated immunity in patients with gastrointestinal carcinoma. Sixty-seven gastrointestinal cancer patients and 42 cancer-free subjects with cholelithiasis as the control group, were included in the study. Serum ACTH, cortisol, TSH, thyroid hormones, IL-6, IL-10 and neopterin levels were measured. Diagnosis and pathological staging were confirmed by surgical intervention. Cortisol levels were correlated with IL-6 in cancer patients. In addition to elevated neopterin values, linear regression analysis revealed that serum neopterin was associated more strongly with the increase of cortisol rather than IL-6 levels in advanced stage carcinoma. Furthermore, neopterin also correlated with IL-6, IL-10, cortisol and TSH levels in advanced carcinoma cases. These data indicated that cortisol, IL-6 and neopterin values of cancer patients were influenced by the tumor presence and progression.