Glycolate is a well-known photosynthetic product of 02-evolving forms of photosynthetic life (2, 4) which is excreted by algae (12) and chloroplasts (10). Conditions which favor glycolate formation and excretion are: high 02 partial pressure, low CO2 tension, and high light intensity. Under these conditions, the oxygenase activity of ribulose-P2 carboxylase forms 3-P-glycerate and 2-P-glycolate (6). The latter is dephosphorylated by a specific phosphatase (9). CO2 and 02 are competitive substrates for this enzyme activity. Experiments with 1802 have demonstrated that it is incorporated into the carboxyl group of glycolate by the action of the carboxylaseoxygenase enzyme (1).The goal of the research reported herein was an attempt to find conditions whereby the photosynthetic formation and excretion of glycolate could be obtained in high yields by algae in an atmosphere of air enriched with a low partial pressure of CO2 rather than a high partial pressure of 02 as employed by many investigators. The glycolate thus obtained could be enzymically converted to H2 for an energy source as depicted in