A secular trend towards higher final height and earlier pubertal maturation is seen in countries with favourable socio-economic development and higher social classes in countries are also associated with taller height and earlier maturation. Environmental factors, such as nutrition and infections, appear to be the main causes for differences in growth and maturation between ethnic and social groups. Differences in final height are mainly due to prepubertal growth. Studies on immigrant children and children adopted into privileged conditions from developing countries confirm the influence of early growth on subsequent growth. Catch-up growth in adopted children could only partially compensate for early stunting, and in several cases was cut short by early pubertal development. A minority developed very early puberty and eventually very short final height. The optimal rate of catch-up growth, the trigger mechanism for early puberty, and the effect of various types of nutritional intervention need to be studied. The studies reported here indicate the critical importance of optimal intra-uterine, infant and childhood growth as a basis for satisfactory growth during adolescence.