Newts (Triturus viridescens) brought to the laboratory during the winter and kept on a limited diet of tubificid worms, developed an anemia characterized by the appearance in the peripheral blood of atypical erythrocytes, known as pseudoerythroplastids. The blood picture did not change after intraperitoneal injections with massive doses of vitamin B12(Merck). Animals collected during the summer did not show this anemia despite limited diet and repeated bleeding. It was suggested that the physiological condition of the newts at the time they are subjected to the anemia-inducing factors, may influence their susceptibility to the production of pseudoerythroplastids.