The Absolute Neutron Activation Analysis (ANAA) technique was used to estimate the reference value for Cl in whole blood of healthy group, selected from blood banks at São Paulo city, to provide information which can help in diagnosis of patients. The results show that the indicative interval obtained for Cl in serum from the nuclear analysis (3.41 - 3.69 µg ·mul-1) is in agreement with the reference value adopted (3.44 - 3.76 µg ·mul-1) in addition, an indicative interval for Cl (2.75 - 2.95 µg ·mul-1) could be proposed for whole blood. The advantages and limitations of using this nuclear methodology were discussed.
