Several observations indicate a possible role of the placental cholinergic system in the modulation and maintenance of placental function and subsequently fetal growth and development. We have investigated the effect of Partusisten (1 mg/kg p.o., twice daily, since the 15th to the 20th day of gestation) on cAMP and cGMP concentrations, acetylcholine esterase and choline acetyltransferase activities in rat placenta. The obtained results show that Partusisten increased cAMP concentration and decreased cGMP concentration (see Tab. 1; Fig. 1, 2). Choline acetyltransferase activity was elevated (Tab. 2; Fig. 3) whereas Partusisten had no effect on acetylcholine esterase activity (see Tab. 2; Fig. 4). The results indicate disorders in placental cholinergic system after chronic Partusisten administration to pregnant rats. On the other hand, the marked increase in choline acetyltransferase activity suggested the high adaptability of placenta.