Plasma oxytocin level was determined by RIA in eight cows with normal parturition or with dystocia and retained foetal membranes. Both concentration and profile of oxytocin measured around parturition in cows with these disturbances were markedly changed, compared to the cows with the normal course of parturition. Oxytocin was released in the greatest amounts during physiological parturition or during parturition with dystocia in response to the Ferguson reflex only. In cows with dystocia lengthen of the period of the low oxytocin level was observed, though cervix was dilated. Then, it seems that some cases of placental retention are related to the low oxytocin level.