Abstract
The spontaneous activity of human myometrial strips obtained during the proliferative and secretory phases of the menstrual cycle and during the early and late stages of pregnancy was studied. Both prostaglandin F (PGF) and oxytocin caused contractions which were superimposed on a low level of spontaneous activity but only PGF was seen to affect high levels of activity. Spontaneous contiactions were ultimately abolished by the addition of indomethacin. The strips remained responsive to PGF but not to oxytocin.