Two groups of five obese female subjects, having undergone a ten day therapeutic fast, were fed with either glucose 50 g/day or with L-alanine 50 g/day for three days. Plasma glucagon concentrations and urinary electrolyte excretion were compared in the two groups. Although 4.00pm plasma glucagon concentrations during refeeding were significantly greater in the alanine refeed group (P less than 0.05) the reduction in urinary sodium excretion in each of the two groups was identical. These observations do not support the hypothesis that glucose induced suppression of plasma glucagon concentrations is a mechanism whereby carbohydrate refeeding produces post-fast urinary sodium retention.