1. γ-l-Glutamyl-l-dopa was given by intravenous infusion to eight normal subjects at doses of 12.5 and 100 μg min −1 kg −1 . 2. Both doses of the dipeptide resulted in an increase in mean urinary sodium excretion. 3. Mean effective renal plasma flow rose at both doses, but mean glomerular filtration rate increased only at the lower dose. 4. There was a fall in mean plasma renin activity after the infusion of both 12.5 and 100 μg min −1 kg −1 . 5. Mean urine free dopamine excretion increased by 280- and 2500-fold at infusion rates of 12.5 and 100 μg min −1 kg −1 respectively. 6. Mean plasma free dopamine rose at both doses but the increase at 12.5 μg min −1 kg −1 was not to a level previously associated with systemic effects of the catecholamine. 7. On administration of the dipeptide at 12.5 μg min −1 kg −1 there were no changes in blood pressure or heart rate, but at the higher dose there was a fall in diastolic blood pressure. 8. At a dose of 12.5 μ g min −1 kg −1 in man, there is kidney specific conversion of gludopa to dopamine.