The Moore's hypothesis concerning a relationship between the metabolism of copper and that of vitamin A led us to consider a possible relationship between this vitamin and ceruloplasmin, the carrier protein for copper. Experiments were carried out on Sprague-Dawley rats. The ceruloplasmin level of control animals and vitamin A - deficient rats was determined An average increase between 22 and 33% was observed in the animals with vitamin A deficiency, the highest levels being observed in the females. These results are in agreement with Peterson's previous work. A second type of experiment was carried out to confirm these results. The rats were raised in a copper-deficient diet and the vitamin A level was regularly determined. In these conditions serum and liver levels of vitamin A are normal and do not vary, ceruloplasmin level is zero; however apoceruloplasmin is still being synthetized : Nevertheless at the ultime state of the deficiency vitamin A level decreases while apoceruloplasmin increases. These results raise the following question. Could the relationship between ceruloplasmin and vitamin A be possibly due to an inflammatory state in vitamin A deficient rats. In this respect a third series of experiments were undertaken and are in progress; the vitamin A and ceruloplasmin levels are regularly determined.