This paper presents data revealing the regulating, equilibrating role of the melatonin-free pineal extract. Administration of this extract lowered statistically significant urinary 17-Ks and cholesterolemia in rabbits and cholesterolemia, hepatic cholesterol and ascorbic acid in the rat under basal conditions. When the initial values of these biochemical indices in the above mentioned animals were below the basal values established, then the pineal extract showed an effect of correction of these values increasing them toward the basal level. Under HCG stimulation total free and esterified cholesterol in the serum and testis as well as the DNA, RNA and proteins in the testicular tissue showed lower values than in the controls. Administration of the extract at the same time with HCG, corrected the HCG-induced lowering effect on these biochemical indices. Similarly, when GnRH induced a decrease and not an increase in serum LH, as expected, the pineal extract played the same regulating role causing rise of serum LH towards the initial values. In one of our experiments in which TRH induced a decrease and not an increase in serum prolactin, the pineal extract corrected this effect. These data suggest an equilibrating role played by the melatonin-free pineal extract in our researches on the pineal gland.