Products of arachidonic acid metabolism (eicosanoids, e.g. some prostaglandins and leukotrienes) have important roles in the maintenance of pregnancy, the mechanism(s) of parturition and various diseases of pregnancy such as pregnancy-induced hypertension. The wealth of literature describing these relationships dictates that the present review be focused rather than global in nature. Only studies of human tissues will be discussed despite the limitations in experimental design that are imposed on such studies. Emphasis will be placed on studies of the cyclooxygenase and to a lesser extent lipoxygenase pathways of arachidonic acid metabolism mentioning only briefly the epoxygenase pathway and catabolic pathways. It should also be noted that many eicosanoids are not derived from arachidonic acid and will not be discussed here. The review of literature will not be comprehensive but rather selective in order to focus on specific issues of importance or controversy. In order to develop concepts of regulation I have focused a section on amnion since this tissue has received most attention for such studies. The significance of the products of the pathways described in the physiologic and pathophysiologic events of pregnancy will be described primarily in a section in which I have attempted to delineate those regulatory mechanisms that are considered most significant in, or specific to pregnancy and parturition. Finally, the reader is dirccted to several excellent reviews that concentrate on areas not emphasized in this review (Keirse, 1979; Challis and Patrick, 1980; Mitchell, 1982; Hammarstrom, 1983; Samuelsson and Funk,1989; Smith, 1989; Myatt, 1990).