Water-extracts of two waste materials, namely chicken manure and blood waste, were used as culture media for the cultivation of Chlorella pyrenoidosa. C. pyrenoidosa had higher growth rates and protein contents when cultivated in these waste materials than had those cultivated in the Bristol medium recommended for the cultivation of green algae. The concentration of the essential elements (i.e. nitrogen, phosphorus and potassium) increased when temperatures during extraction increased. The growth rates of C. pyrenoidosa in the extract of the blood waste prepared at 0°C and the extract of chicken manure prepared at 62°C were similar. It is suggested to construct algal ponds near industrial areas for the dual purposes of purifying waste effluent and of producing edible protein. Copyright © 1981 Published by Elsevier B.V.