Modulation of cervical secretion at ovulation time was studied in 10 women with regular menstruations. In an in-vivo model with repeated collection of mucus samples during three 90-min periods, the amounts of mucus in a control cycle and in three experimental cycles were compared. Drugs interacting with the autonomic nervous system and a prostaglandin synthase inhibitor were administered at time of ovulation. The cholinomimetic drug carbacholine significantly increased cervical secretion, while the anticholinergic drug butylscopolamine markedly inhibited this secretion. A long-lasting decrease in secretion was seen after administration of the prostaglandin synthase inhibitor diclofenac. Beside regulation of cervical secretion by the ovarian hormones, these results suggest an autonomic nervous modulation of cervical secretion, and in addition an impact on cervical by a prostaglandin synthase inhibitor. The effects on fertility regulation in the female are discussed.