Some of the most important types of small and tall stature which are accessible to treatment are discussed. The causes of small stature are multiple, since any severe chronic illness during childhood may inhibit growth and the most specifically treatable disorders (e.g. hypothyroidism and hypopituitarism) are the least frequent ones. In tall stature, the causes are less varied and genetically determined, familial tall stature is predominant. The point is stressed that the basis of an accurate diagnosis in these conditions is (1) a thorough understanding of the dynamics and variations of normal growth and (2) knowledge of methods concerning growth analysis, evaluation of bone maturation and prediction of adult height. Sophisticated laboratory procedures, such as determinations of growth hormone, are necessary in only a few selected cases.