The bilateral removal of the superior sympathetic cervical ganglion was performed on rats bearing anovulatory syndrome with persistent vaginal cornification and poly-follicular ovaries caused by frontal hypothalamic deafferentation. After cervical sympathectomy, an irregular but evident cyclicity of the vaginal smears returned, and the animals ovulated again in a cyclic manner and became pregnant; the pregnancies were normal as regards duration, deliveries and number of litters. Shamganglionectomy failed to influence the persistent vaginal oestrous and the poly-follicular state of the ovaries. The melatonin secretion seems to influence the hypothalamic mechanism which controls the periodical release of LH.