Expression of the vasopressin and oxytocin genes has been described so far only in the hypothalamus. We report here that at least the oxytocin gene is highly transcribed in the bovine corpus luteum during the mid-luteal phase of the oestrous cycle. Luteal cDNA sequence analysis as well as cell-free translation studies showed that the luteal mRNA is essentially similar to that in the hypothalamus, except that in the corpus luteum the poly(A) tail of this mRNA is shorter. When calculating the relative amounts per organ, the active corpus luteum produces approximately 250 times more oxytocin mRNA than a single hypothalamus.