The present study was conducted in order to test the hypothesis the elevated cytokine levels in amniotic fluid from normal deliveries may be generated by a subclinical inflammatory response in intrauterine tissue. Specimens were collected from 38 women with normal deliveries. The levels of tumour necrosis factor, IL1 and IL6 in amniotic fluid samples correlated with the extent of inflammatory cell infiltration in specimens of the foetal membranes, placenta and umbilical cord. Tumour necrosis factor, IL1 and IL6 are generally produced as part of the inflammatory reaction and stimulate synthesis of prostaglandin. Thus a subclinical, intrauterine inflammatory response may play a role in initiation of normal parturition at term.