Abstract: An intravaginal or intrarectal electrode for electro-stimulation and/or biofeedback monitoring of muscle activity, which electrode comprises a pair of electrode lines each comprising a lead 10, 11 with an electrode terminus 7, 7' and a probe body 1 having an enlarged head portion 2 to seat within the vagina or rectum or the rectum and having at least one longitudinal convex surface 5, 7 extending for a majority of the length of the probe body 1 head portion and carrying at least one of the electrode termini, a narrower neck portion 3 adapted to seat at the introitus of the vagina or of the rectum and handle means 4 extending from the neck portion 3 to enable the probe body 1 head and neck to be inserted into and withdrawn from the vagina or the rectum.