A completely synthetic medium containing amino acids, nucleic acid derivatives, vitamins, salts, and glucose for the maintenance of schistosomes in vitro is herein described. This medium appears adequate for short-term survival of these parasites, since they can be kept alive for periods somewhat more than a month. During early in vitro maintenance, the worms lay eggs and otherwise demonstrate normal behavior patterns. However, after about 20 days they begin to deteriorate, indicating that this artificial medium is far from optimal.