Puberty is a maturational process of the hypothalamo-pituitary-gonadal axis resulting in growth and development of the genital organs and concomitantly physical changes. All these changes are the result of an increasing activity of the pituitary and consequently of the gonads caused by increased stimulation by the luteinizing hormone-releasing hormone (LHRH). Delayed puberty is a common problem in contrast to true hypogonadotropic hypogonadism. Since a few years pulsatile LHRH administration is applied to induce pubertal development in hypogonadotropic boys. Except for virilisation, development of the testes including spermatogenesis can be achieved. In contrast to boys, substitution with sex steroids brings about a satisfactory physiologic development of the sex characteristics in girls. The physiology and disorders of pubertal development as well as this new LHRH treatment to induce puberty will be discussed in this paper.