Feather-sexed broiler chickens were fed rations based on corn-soybean meal combinations. Both sexes received a diet containing 24% crude protein and 3100 kcal ME/kg of feed from 0 to 14 days of age. From 32 to 45 days, males were given a 20% protein and 3200 kcal ME/kg feed while females were offered 16% protein at the same caloric level from 32 to 52 days. Increasing supplemental methionine in the starting diet containing 2.1 g cystine/16 g N led to an improved feed conversion as the only response, and the .46% level of methionine (1.92 g/16 g N) proved optimal for both sexes. Each finishing diet had the same level of cystine relative to protein as the starting ration and the need for methionine at this stage of development approximated 1.84 g/16 g N, which was comparable between the sexes. Difference in bled and plucked weights upon processing did not indicate any alteration in feather cover due to methionine.Repeating the experiment with methionine being fixed at previously determined optimum levels and progressively increasing dietary cystine led to sex differences for both starting and finishing stages of development. Males exhibited an improved feed conversion from 0 to 14 days at a lower cystine level than females (.41%, 1.71 g/16 g N vs. .46%, 1.92 g N/16 g). The converse appeared during finishing (2.25 vs. 2.00 g/16 g N) where the only parameter affected was feather quantity. Differences in feathering rate because of strain, sex, and age could explain a large part of the variability in determined sulfur amino acid requirements.