During fetal development, androgens exert long-term effects which are either organizational on specific organs during a critical phase of morphogenesis (e.g. sexual differentiation of external genitalia), or programming neural functions or enzyme activities expressed later in life. At all stages of development, which extends from fetal and neonatal stages to pubertal accomplishment, androgens also have activational effects that are immediate, multiple, reversible and dose dependent. Both types of actions are intricate during human development. This review will focus (1) on the intricate morphological and activational roles of androgens on sexual differentiation and pubertal development of the genital tract, external genitalia and mammary glands, and (2) on the organizational effects of androgens on four central nervous system functions: pituitary regulation of liver metabolism, gonadotropin secretions, sex dimorphic behavioral patterns, and ‘sexualization of the brain’. If the molecular basis of the immediate androgenic action is known, depending of androgen receptor’s availability and affinity, little is known of the way androgens exert their influence on either so various morphological processes or neuroendocrine imprinting.