The studies were performed on intact and pregnant rats after the administration of 10(-2) U of oxytocin. Oxytocin-induced increase in spasm duration and microvascular dilatation was noted both in intact and pregnant animals. However, in the former case spasm duration was markedly increased, while in the latter case there was an equal increase both in spasm duration and dilatation. Dilatation phase was characterized by an increase in microvessel diameter, as compared to the initial one. Maximal spasm phase after oxytocin administration in intact rats was characterized by hemostasis. In pregnant animals blood flow was delayed, with no marked spasm present. The initial level of microcirculation was restored 38-40 minutes later.