Summary 1. Serial examinations in growth studies of children should include assessments of physical maturation as well as of physical growth. 2. In the cases here reported, the W.R.U. standards of physical maturation, assessed on roentgenograms of the skeleton, are employed because they permit greater precision of assessment than the standards put forward by other workers. 3. Illustrative instances from our studies of aberrant growth are here presented to demonstrate the tempo of progress before and during treatment for developmental growth promotion. 4. Two boys are chosen from our series of retarded adolescence. Their progress in developmental growth for two years preceding active intervention is presented and with this is presented their progress during six months of endocrine treatment devised to hasten an adolescence already considerably delayed. It is not intended to suggest that, lacking treatment, these boys would not ultimately have matured but it is contended that developmental growth metabolism has been favored and stature probably increased by treatment. 5. A third case is presented in some detail to illustrate how adjustment of dosage and proper care in the utilization of extracts from the different endocrine glands permit one to promote increase of stature or progressive maturation as serial assessment of the case may require. The case chosen (SS 2895) is a relatively simple form of retarded developmental growth in which thyroid and pituitary substances were adequate to promote satisfactory results since the deficiency was uncomplicated by actual defects due to chronic disturbance of growth, to long continued focal infection, or other constitutional mutilation. It must not be assumed that every case treated will resolve so readily or display so marked a sensitivity to modifications in the régime of treatment as is so beautifully demonstrated in SS 2895.