Attempts were made to purify the LH-releasing substance extracted from the leaves of Avena sativa by means of two-step chromatographic procedures using a weakly acidic ion-exchange resin (CC-50, type II) and DEAE-Sephadex A-25 (coarse) with successful results. For preliminary fractionation of such starting materials as dried leaves, fresh leaves, and acetone-extracted powder (crude extracts), 5% acetate-buffered active carbon proved to be more effective than starch zone electrophoresis. From its behavior on chromatography with weakly acidic ion-exchange resins as well as Sephadex gel filtration, the active fraction extracted from the leaves of Avena saliva was assumed to be different from the LH-RH present in the hypothalamus. This partially purified material, however, was demonstrated to have an LH-releasing activity by the ovarian ascorbic acid depletion method using Wistar-Imamichi strain rats. Evidence was presented that its site of action is in the adenohypophysis.