Numerous recent studies demonstrated that electrical stimulation of the periaqueductal gray matter (PGM) can result in powerful analgesia to pain of somatic origin. In the present study, we have developed a visceral pain test employing intraperitoneal injection of hypertonic saline which yields a writhing response in the adult rat more reliably than other pain-producing substances. With this test we show that writhing as well as the response to radiant heat (tail flick test) are completely inhibited in all animals with PGM electrode placements.