The blood plasma ascorbic acid (reduced form) in active cases of rheumatoid arthritis is regularly low if the individuals have not been maintained on a high vitamin C supplement. Unadvised cases were found to show uniformly lowered levels. The reduction is striking. Such levels rise in response to extra supplements of vitamin C. In many this rise is refractory. Our studies indicate that in some cases the intake required to maintain adequate vitamin C levels in the plasma are much above the average requirement for normal individuals. The mechanism involved is unexplained.