The progesterone, androstenedione and oestradiol contents of the theca and granulosa tissues of the four largest follicles in the ovarian hierarchy of the hen were determined. The granulosa tissue contained significantly (P less than 0.05) more progesterone and less androstenedione and oestradiol than the theca tissue. The content of progesterone was greatest in the granulosa tissue of the first three follicles in the hierarchy and in each of these follicles there was a peak in progesterone content of the granulosa 4 h before ovulation. The theca of the second, third and fourth follicles and the granulosa of the third and fourth follicles contained significantly (P less than 0.05) more androstenedione than either tissue in the largest follicle. The content of androstenedione was maximal approximately 8 h before ovulation in both tissues of the second and third follicles. The content of oestradiol in the granulosa did not vary as follicles changed position within the hierarchy or during the ovulatory cycle. The oestradiol content of the theca tissue remained constant during the third and fourth positions in the hierarchy and declined throughout the second and first positions until a nadir was observed approximately 20 h before ovulation. It was concluded that the synthesis of androstenedione and oestradiol ceases in both follicular tissues after the follicle is exposed to the penultimate preovulatory surge of LH and that progesterone production is stimulated in the granulosa of the three largest follicles at the time of the preovulatory release of LH.