U-14C-Leucine uptake and eliminaton in connection with morphological investigations after sublethal doses have been studied. The tracer uptake and elimination curves do not show significant differences between controls and irradiated animals, except for early appearance of initial peaks. An increased uptake of labeled amino acid was observed only 32 and 120 hours after irradiation, when sacrifices were done at the same hours of the day. The dose employed does not seem to affect in any significant way either the acinar and duct cells or other structures. Only a mild thickening of the connective tissue has been observed in the parotid of animals sacrificed at longer intervals.