SUMMARY Separation and partial purification of chicken pituitary follicle-stimulating hormone (FSH) and luteinizing hormone (LH) has been obtained by methods which were effective in the purification of the corresponding human and horse hormones. Increases in chicken LH activity were observed after chromatography on DEAE-cellulose and on Amberlite IRC-50 suggesting removal of an LH inhibitor. The biological potencies of chicken FSH and LH preparations when assayed in mammals were very much lower than those of the corresponding mammalian fractions on a weight basis. A weak immunological cross-reaction between chicken and human pituitary LH was used to estimate LH in chicken pituitary fractions and the results were compared with bioassays of the same fractions.