The mean blood content of interleukin-6 in patients with adrenal tumors was much higher than in healthy donors. No correlations were revealed between interleukin-6 level, patients sex and age, stage and duration of the disease. Interleukin-6 concentration was maximum in patients with adrenocortical cancer. A negative correlation was found between interleukin-6 level and blood cortisol concentration in patients with cortisol-producing adenoma. In patients with aldosterone-producing adenoma, interleukin-6 level tended to correlate negatively with plasma renin activity.