Sixteen presumably hypopituitary dwarfs and 4 hyperpituitary giants were followed from 1 to 13 yrs. through periods of treatment and control. Data are analyzed particularly from the longitudinal viewpoint. Growth of dwarfs and giants shows contrasts similar to the contrasts that are seen between early- and late-maturing normals. In growth rate dwarfs tend to have low rates with late adolescent spurts, sometimes of considerable magnitude; giants have high rates with early spurts. In stature and skeletal development dwarfs fall further behind normal before their adolescence and recover gradually thereafter. Inversely, giants show pre-adolescent acceleration with subsequent return toward normal. When sitting height: stature ratios are noted, dwarfs tend to be short-legged; giants may be long-legged'' before adolescence, short- or medium-legged afterwards. Basal metabolic rates have a surprising distribution; many dwarfs have rates above normal; giants, below normal. It is suggested that this may be because, under certain circumstances when growth is more rapid, proportionately less O2 is used during the basal metabolic test. Conversely, intelligence quotients tend to be low in dwarfs, high in giants. Sexual maturation tends to retardation and incompleteness in dwarfs, to acceleration in giants. Observations cover periods of treatment with thyroid, growth hormone, and sex hoimones. The outstanding finding is that it is very difficult to evaluate treatment during adolescence, because during adolescence in both dwarfs and giants, the natural growth pattern often supersedes the effects of any treatment. In dwarfs, thyroid most consistently stimulated all phases of growth, showing the usual clear effect on skeletal maturation. Thyroid and growth hormone appeared to reinforce each other in stimulating growth rate. One growth-stimulating effect of sex hormone in a dwarf and one maturing effect in u giant encourage further trial with sex and sex stimulating hormones.