In the human fetus and in the early postnatal period, during development, the total body taurine content, particularly of the brain, increases markedly. It can be estimated that the human fetus accumulates approximately 50-60 mumol/24 h during the last 4 weeks of pregnancy. As there is evidence for the relative inability of infants to synthesize taurine, this nitrogen compound has to be wholly supplied by the mother during pregnancy and by diet after birth, particularly for the prematures who have to constitute appreciable reserves in their tissues. In adults (mammals and humans), it has been shown that the slowly exchangeable pool of taurine (mainly brain and muscles) cannot be increased by exogenous taurine but, in growing mammals, taurine from diet is rapidly transferred to tissues. Although no real proof yet exists, it seems probable that taurine should be considered an essential nutrient for premature infants.