The inter-relationship between the pituitary and the gonad has long appeared too complex to be regulated solely through the mediation of the two pituitary gonadotrophins, follicle-stimulating hormone (FSH) and luteinizing hormone (LH). Within the last decade, discoveries of additional regulatory mechanisms involved in the neuroendocrine control of the testis and ovary have provided new insight into the control of this sophisticated biological phenomenon. The possible contribution of inhibins and activins to the hypothalamo–pituitary–gonadal axis, and their role as paracrine regulators in the testis and ovary have received increasing attention over the years following their isolation and sequencing. This review will assess current knowledge concerning the endocrine and paracrine actions of inhibins and activins in the reproductive biology of the male, with particular attention being paid to possible cross-species differences in function.