Plants used by Southern African traditional healers for the treatment of menstrual pains were screened for prostaglandin-synthesis inhibitors and the ability to reduce isolated uterine muscle contraction using the cyclooxygenase and in vitro uterine bioassays respectively. Prostaglandins are synthesized from arachidonic acid and the enzyme that drives this reaction is cyclooxygenase. The excessive production of prostaglandins by the myometrium and endometrium induces uterine contractions. Inhibition of cyclooxygenase and hence of the prostaglandin biosynthetic pathway may lead to relief of menstrual pain. Ten plants used by traditional healers for menstrual pains were assayed for cyclooxygenase inhibitory activity. Several plant extracts exhibited high inhibitory activity in the assay. The highest activities were obtained with ethanolic extracts of Siphonochilus aethiopicus, Cenchrus ciliaris and Solanum mauritianum. Generally ethanolic extracts gave higher activity than the aqueous extracts. None of the ethanolic plant extracts were able to relax or reduce the contractions of the precontracted guinea pig uterus.