In contrast to vertebrates and to bacteria, relatively few investigations have been carried out on the metabolism and the nutrition of Protozoa. Such information is scattered widely throughout the zoological, parasitological, microbiological, physiological and biochemical literature. Therefore, the recent book on the biochemistry and physiology of protozoa, edited by A. Lwoff, is to be welcomed because it summarizes and reviews the present status of our knowledge in this field. Also, it undoubtedly will stimulate further much needed research on these problems. As stated by A. Lwoff in his introduction, some biochemists who had been “forced during World War II to cooperate with parasitologists in the study of parasitic protozoa were anxious to return to studies on muscle or yeast. For the future development of protozoan biochemistry, it seems of utmost importance that an atmosphere develop in which more biochemists may feel, without external pressure, that many problems of biochemistry of Protozoa are now ripe for further investigations” and are “quite ready to respond to their love and interest.”