Ovine pineal glands (PGs, n = 168), cerebral cortex(C) and stalk-median eminences (SMEs) were obtained fresh from slaughterhouse sheep and mature ewes during the estrous cycle. Tissues were extracted in 2N acetic acid (aa) followed by either glacial aa or ethanol. Portions of the preparations were further subjected to gel filtration using Sephadex G-25. Neutralized extracts were assayed for LHRH using radioimmunoassay. LHRH immunoreactivity was consistantly detected in the various extracts, ranging from 7-150 pg/PG (0.1-1.7 pg/mg), 0.1-0.3 pg/mg C and 35-72 ng/SME (0.7-1.4 ng/mg). Slopes of binding displacement regression lines for the preparations were not different from that of synthetic LHRH. Chromatographic elution profiles for preparations of SMEs and PGs were similar and the bulk of immunoreactivity eluted in a position coincident with that of synthetic LHRH. Immunoreactivity in cortical extracts ran in advance of the others. PG contents of LHRH immunoreactivity were similar during the estrous cycle.