Twelve different human growth hormone preparations used concurrently for the treatment of pituitary dwarfism have been studied by gel filtration and radioimmunoassay for GH, FSH, LH and TSH. The GH content of the vials as stated by the manufacturer could be verified by radioimmunoassay in all but one preparation that contained much less than indicated. All preparations which had been extracted from acetone-preserved glands by various methods were shown to contain large amounts of aggregated growth hormone. By contrast, preparations extracted from frozen pituitaries contained GH mainly in the native monomeric form. FSH, LH and TSH could be detected in all preparations. With the exception of one preparation containing large amounts of all three glycoprotein hormones, the degree contamination of these hormones was moderate to low. No conclusion could be drawn from the content of glycoprotein hormones as to whether frozen glands or pituitaries preserved in acetone were used as raw material. The advantage of using growth hormone prepared according to the Roos method, or any modification of it starting from frozen glands, over preparations made from glands preserved in acetone is discussed. (J Clin Endocrinol Metab40: 856, 1975)