The effect of feeding different lysine and metabolizable energy (ME) levels to 1221 crossbred Large White × Landrace developing gilts housed in groups from 100 d of age until slaughter (approximately 260 d of age) on age at puberty and reproductive tract measurements were evaluated. Gilts were randomly allotted to six corn-soybean diets formulated to provide two standardized ileal digestible lysine levels [100% (high, HL) and 85% (low, LL)] and threemetabolizable energy levels [ME, 90% (low, LME), 100% (medium, MME), 110% (high, HME). Average age at puberty was 193 d of age. There were no effects of the dietary treatments on age at puberty or any of the reproductive tract measurements. Despite significant differences in the lysine:energy ratio in the diets, the expected differences in reproductive traits were not observed. Other factors such as body weight (BW) and days of estrous cycle had a greater effect on the traits recorded than feed provided.