Alanine metabolism in 24 hour starved 20-day pregnant rats, following intravenously administered C14-alanine, in trace dose that does not affect the normal availability of this amino acid, has been studied. The steady state levels of alanine and glucose in blood, liver and skeletal muscle, together with the tissue glycogen, metabolites and amino acid composition pools, are given in both the maternal and foetal compartments compared with the virgin control rats. The utilization of alanine as a gluconeogenetic precursor is not increased in late pregnancy under 24-hour starvation and it depends on the lower blood substrate availability.