Abstract Brains from scorbutic and ascorbic acid supplemented guinea pigs were used as a source of enzyme for decarboxylation of [1-14C-]-2-hydroxytetracosanoic acid. Both in the 10,000xg supernatant fraction and the recombined 110,000xg pellet and supernatant fractions, decarboxylation was greatly reduced. In the latter experiments, the loss of activity was largely due to the supernatant fraction, which contains most of the brain ascorbic acid. Ascorbic acid supplementation, both in vivo and in vitro restored enzymatic activity in the preparations from scorbutic animals, but, in vitro , did not affect the preparations from the supplemented animals.