The concentrations of free amino-acids have been determined in 54 samples of human milk: 18 in colostrum, 18 in transition milk and 18 in mature milk, all of them taken from women in the Eastern part of Andalucía. The amino-acids have been determined through high pressure ion-exchange chromatography and fluorimetric detection. Glutamic acid is the major free amino-acid, representing 21-52% of the total amount of these components in human milk. Its level increase significantly with advancing lactation. Taurine represents 14-19 of total free amino-acids in human milk, remaining its levels practically unchanged during the whole lactation. The fact that the major content of essential free amino-acids in present in human colostrum could suppose a contribution of these substances which are directly absorbable during a period of life when the nutritional requirements of the neonate are incremented.