Effects of continuous intramuscular administration of the lipoidal and aqueous extracts of the wall of the largest preovulatory follicle (3·8–4·0 cm), to chicks from 11 to 29 weeks on alternate days have been studied on the ovarian growth, follicular growth and atresia, and the onset of ovulation. The lipoidal and aqueous extracts appear to have antagonistic effects on the follicular growth and atresia. Chicks injected with lipid extract show increased ovarian weight, enhanced follicular growth and egg laying started at 22nd week which is earlier to 25th week in control birds. The onset of egg laying was delayed in chicks injected with aqueous extract of largest follicle wall by 4 weeks as compared to control birds. Their ovaries showed decreased rate of follicular growth and increased follicular atresia as a result of which abundant amount of lipid-rich interstitial gland tissue of thecal origin accumulates in them.