Large doses of N-dichloroacetyl-dl-serine sodium salt were required to cause regression of Sarcoma-37 in mice. About 56% of the unchanged compound was recovered from the urine. These observations suggest that the antitumor activity may reside in a metabolic product of the N-dichloroacetyl serine. It is postulated that the active compound is the corresponding O- dichloroacetyl-dl-serine formed from the N-acyl compound by an in vivo enzymatically ...