Five products of the dynorphin gene-cY-neo-endorphin, P-neo-endorphin, dynorphin A, dynorphin A-(1-8), and dynorphin B-were measured in various regions of rat brain and in rat spinal cord and pituitary. Specific antisera were used, supplemented by gel permeation analysis and high performance liquid chromatography, confirming the presence of dynorphin-32, dynorphin A, and dynorphin B in rat brain. In whole brain, a-neo-endorphin, dynorphin A-(1-8), and dynorphin B are present in much greater amounts than P-neo-endorphin or dynorphin A. Although a general parallelism was found in the distribution of the five peptides, there were also noteworthy exceptions, suggesting that differential processing may occur.