The intracerebroventricular administration of 0.15 and 1.5 nmol ovine corticotropin releasing factor (oCRF) to freely-moving adult male rats resulted in a dose-related inhibition of spontaneous GH secretion. This inhibition lasted for at least 3 h and was statistically significant at all time points. By contrast, the iv injection of 1.5 nmol oCRF was without effect. These results suggest that CRF can act within the central nervous system to interfere with spontaneous GH secretion.