With the recent remarkable development of transportation facilities, pregnant women are frequently exposed to mechanical vibration. To experimentally demonstrate that vibration disorders normal pregnancy, uterine blood flow (UBF) and the several kinds of endocrine indicators were examined in pregnant rats exposed to vibration (10m/s2, 8Hz, 90 min). The exposure to vibration decreased UBF in the rats significantly. The UBF of the rats pretreated with peritoneal administration of angiotensin II (AII) was increased when they were not exposed to vibration. In contrast to this, in AII pretreated rats simultaneously exposed to vibration, a significant decrease in the UBF was recognized. Vibration decreased the plasma level of progesterone (PRO), but pretreatment with AII induced no difference in PRO in vibration-exposed and unexposed rats. The level of prostaglandin E2 (PGE2) was decreased in rats exposed to vibration, but not in control rats. Pretreatment with AII still decreased PGE2 in rats exposed to vibration. These results indicate that vibration may play an important role in the development of abnormal pregnancy through uterine circulatory and ovarian dysfunctions. It seems that a decrease in UBF is induced primarily via an inhibitory effect of vibration on PGE2, and secondarily via a direct action on the uterus.