A study on the utilization of inorganic sulfur in chicks was carried out with labeled sulfate-sulfur fed to five-day old chicks and radioactiviy was counted for various tissues and organs of chicks after one to four weeks of treatment. Tendomucoid prepared from trachae and collagen made from esophagus and tendon emitted the beta-ray with a considerable variation between tissues and between treatments throughout the investigation indicating that these tissues incorporated labeled sulfate into sulfate-containing compounds. A similar observation was made on the elastin prepared from wing and leg skin suggesting a probable conversion of sulfate sulfur to organic sulfur such as cystine and methionine. The ray was detected from the feather of both wing and tail from the first week till the fourth week of the experiment. This is definitely indicative that inorganic sulfur is incorportated into cystine, an amino acid which alone counts more than 20 per cent of total amino acids in feather. Total homogenates made from liver, kidney, heart and breast muscle during the third and fourth treatments also emitted radioactivity.