Rats euhydrated, dehydrated for two days or haemorrhaged were given intracerebroventricularly (i.c.v.) luteinizing hormone releasing hormone (LH-RH) in a daily dose of 100 ng dissolved in 10 microl of 0.9 % sodium chloride. In euhydrated rats, a single i.c.v. dose of LH-RH as well as the daily i.c.v. treatment with LH-RH for two days did not affect significantly either the plasma oxytocin concentrations or the hypothalamo-neurohypophysial oxytocin content. In animals dehydrated for two days and treated with LH-RH the increase in plasma oxytocin was almost suppressed and the depletion of neurohypophysial hormone content was significantly less marked. Luliberin treatment had no effect on the hypothalamo-neurohypophysial content of oxytocin as well as on plasma oxytocin concentration in haemorrhaged rats. We suggest that LH-RH may have a regulatory role in the hypothalamo-neurohypophysial oxytocinergic system, especially under hyperosmotic dehydration.