The effects of estradiol-17$eta$ and progesterone on the spontaneous motility of pig oviductal isthmic smooth muscle were investigated. The motility of the Isolated smooth muscle was recorded by using physiological recording system. The results were summarized as follows; 1. The amplitude and frequency of spontaneous motility in pig isthmic smooth muscle were 0.251$pm$0.023 g and 15.380$pm$0.935/min in follicular stage, and 0.201$pm$0.027g and 14.520$pm$1.382/min in luteal stage. 2. The spontaneous motility of pig isthmic smooth muscle was excited by estradiol-17$eta$ but was not by progesterone in follicular and luteal stage.