The relationship between serum cortisol and fasting blood sugar levels in 39 female patients with endogenous depression was studied. Serum cortisol levels were determined in two post-dexamethasone blood samples during the dexamethasone suppression test. There were no significant differences between the blood sugar levels of suppressors (patients with low serum cortisol level) and non-suppressors (patients with high serum cortisol level). There was no correlation between the serum cortisol levels and blood sugar values in these two groups either. Although numerous reports claim to have found a relationship between endogenous depression and diabetes mellitus, our data do not imply a direct relationship between serum cortisol and blood glucose levels of endogenously depressed patients.