The posthatch profiles of plasma immunoreactive inhibin and gonadotropins (FSH and LH) were examined in male and female chickens. Blood samples were collected and hormones were measured by radioimmunoassay at biweekly intervals from Week 1 through Week 19 (Week 21 in females) posthatch. Immunoreactive inhibin was elevated (P< 0.01) in males between Weeks 7 and 15. In contrast, immunoreactive inhibin was significantly elevated (P< 0.001) in females at 17 and 19 weeks compared to earlier time points. There was no significant difference in FSH level between males and females. Both sexes showed a significant (P< 0.01) rise in FSH during development. Males had significantly higher levels of LH compared to females. While there was no change in LH throughout 19 weeks in females, plasma LH was significantly elevated in males at 7, 11, 13, and 15 weeks. Results suggest that a negative relationship between inhibin and FSH may be established in females, in contrast to males, at the onset of puberty.