Stressful stimuli are known to inhibitthe secretion of radioimmunoassayable rat growth hormone (RGH). Groups of adult male rats submitted to one of three different types of hypothalamic deafferentation (total, incomplete, or frontal) were exposed to ether and auditory stresses at 1 week intervals. Ether and auditory stresses were equally effective in inhibiting the RGH secretion in controls and frontally deafferented rats. Ether stress inhibited the RGH values of completely deafferented animals, while auditory stress left these values unchanged; α-MT pretreatment blocked the effect of ether stress in such animals. Neither stress was able to modify the already low values of the incompletely deafferented rats; pentobarbital anesthesia induced a marked rise of RGH plasma levels in these animals. Base-line levels of RGH were significantly higher in frontally deafferented, and significantly lower in incompletely deafferented rats than those of controls. These data seem to indicate that ether stress is transmitted through a humoral, dopa-minergic pathway, while auditory stress follows a nervous pathway. In addition, extra-hypothalamic influences seem to modulate the secretion of RGH through frontal inhibitory and postero-lateral stimulatory nervous pathways.