This research was conducted to establish a temporal hormone profile in genetically selected populations of roosters differing in sexual activity. Plasma levels of androstenedione (AE), dihydrotestosterone (DHT), testosterone (T), total androgens (Total A) and estradiol-17_β (E₂) were measured at 1, 56, 112 and 168 days of age by radioimmunoassay. No significant differences in mean hormone values were found between the lines at any age. Temporal hormonal patterns for each hormone were also similar for the lines. The levels of AE, T and Total A were observed to increase from Day 1 to 56, stabilize at Day 112, and rise again prior to Day 168. Dihydrotestosterone levels were relatively low throughout development but did show increases by Day 168. Estradiol-17_β concentration did not change significantly with age. The percentage of variation attributable to sire family was determined. No consistent differences between sire families within a line were observed. Within line correlation analyses were calculated between each of the hormonal traits. A higher incidence of significant correlations was observed among the high mating line suggesting these animals have a more uniform hormonal state throughout development as opposed to the low mating line. Packed cell volume and body weight measurements were obtained at the termination of the experiment. Significant differences were found between the mating lines for both characteristics; the high mating line exhibited a greater mean packed cell volume and a lesser mean body weight. / Master of Science