This study investigated the effects of eighteen L-amino acids on the growth and biochemical composition of Chlorella pyrenoidosa. Under the nitrate deficiency condition, ten L-amino acids were found to exert stronger stimulative effects on the algal growth than the other amino acids. After 10-day culture, addition of 0.5 g L (1) the above mentioned ten amino acids significantly increased the cellular protein contents by 441.3-110.8%, respectively, and significantly decreased the carbohydrate contents by 60.7-16.2%, respectively. Under the normal nitrate condition, the cellular biochemical composition was not significantly affected by addition of serine, leucine, proline, aspartic acid, asparagine, and glycine, whereas addition of aspartic acid and arginine increased the algal biomass by 110.2% and 62.8% compared with the control. Finally, the significance of this work in the biotechnological application of culturing C. pyrenoidosa in organic wastewater rich in amino acids was further discussed. (C) 2015 Published by Elsevier Ltd.