1. 1. Chlorella pyrenoidosa utilizes both nitrogen atoms of glutamine for cell synthesis. Glutamic acid when present in a complete culture medium is not utilized for growth. 2. 2. Experiments with [ 14Cglutamine showed rapid conversion of glutamine to glutamic acid within the algal cell. Examination of the radioactive compounds formed indicates that this glutamic acid is further utilized via incorporation into the tricarboxylic acid cycle. Glutamic acid is also shown to be a precursor of proline. 3. 3. Non-utilization of externally fed glutamic acid as related to non-penetration of the cell wall is considered. Utilization of δ-carboxyl substituted glutamic acids and the influence of dimethyl sulfoxide on penetration is discussed.