To the Editor. —In the December 1970 issue, my associates and I (126:983-989) presented data on Candida at Boston City Hospital, and included results of in vitro tests of the activity of flucytosine (5-fluro-cytosine, 5-FC) against isolates of Candida which indicated that this drug was not active in the medium and by the test employed. This agent has been shown to be a well-tolerated and often effective oral antifungal drug. I hope, therefore, that you will reproduce the relevant portion of the enclosed letter from Dr. Jan Schonebeck who recently published a monograph on the subject ( Scand J Urol Nephrol , suppl 11, p 48,1972) and several other papers in the same journal in the last two years, presenting evidence of the antifungal activity of flucytosine. In some of these papers, he also demonstrated development of high degrees of resistance of yeast and fungi in vitro and during treatment, and therefore