Five human term placentas were analyzed for total free amino acid concentrations. Calculation of tissue fluid distribution via 14C inulin space enabled an estimation of placental intracellular amino acid concentrations based upon cord and maternal plasma concentrations. Maximum and minimum estimates for amino acid concentration in intracellular water are given. Data are compared to concentrations in organs of various species. Taurine was present in the highest concentration (3.529±1.120 μmoles per gram wet weight). Glutamic and aspartic acids, alanine, glycine, and glutamine were all present in concentrations greater than 0.5 μmoles per gram wet weight.