Decanoic hydroxamic acid (DHA) was markedly inhibitory to growth of certain fungi, both mycelial and yeast-like. Quantitatively, it was approximately 4 times as active as the unsubsti-tuted acid on Candida albicans. Activity was apparently not mediated through a release of free hydroxylamine. Toxicity upon parenteral administration to experimental animals was not primarily to liver, spleen, bone marrow, or kidney. Topical application of 1% DHA in propylene glycol on patients with cutaneous C. albicans infections caused considerable regression of lesions in one week. No evidence of sensitization or primary irritation was observed in this group.