The effect of a glutamine force-feeding on plasma amino-acid levels in rats fed either a reference diet or a cafeteria diet was studied during weaning. The increases in plasma amino-acid levels shown by rats eating the cafeteria diet were related to the force-feeding and/or the age studied. The glutamine solution decreased the levels of proline, ornithine and tyrosine in the plasma of rats eating the cafeteria diet. In rats fed the reference diet, glutamine solution increased the plasma concentrations of threonine and cysteine. A major effect of diet over force-feeding was shown.