Specific gonadotropin receptors of the rat testis were purified 15,000-fold after detergent extraction by a single affinity chromatography step on agarose coupled to human chorionic gonadotropin. Receptors were eluted in the free form at pH 3.2 and did not aggregate in the absence of detergent. The purified receptors displayed about 50% of the maximum theoretical binding activity, and retained the high binding affinity and hormonal specificity of the original gonadotropin receptors of the cell membrane.