The description of vasoactive intestinal peptide (VIP) immunoreactivity in the rat anterior pituitary gland has stimulated much interest in possible autocrine and/or paracrine roles as well as in the regulation of its biosynthesis (1-6). The detection of two VIP transcripts in this tissue, together with the knowledge of the rat VIP cDNA sequence (7), has led us to speculate that they are products of the same gene but as a result of differential transcriptional termination, differ in the length of the 3'untranslated region. In this study, we present evidence for the differential utilization of poly(A) addition sites which accounts for the generation of two distinct VIP RNA species.