Human endometrium undergoes sequences of proliferation, and secretion followed by menstruation in a predictable fashion. The importance of systemic factors, steroid hormones, in driving endometrium through these phases is well known. However, it is becoming increasingly apparent that a group of factors collectively called cytokines may also serve a key role as local modulators of endometrial function. Expression of the receptors for cytokines, production of cytokines and the ability to demonstrate modulation of a host of functions of both endometrial epithelium and stroma indicate that human endometrium is uniquely poised to respond to cytokines.