Some recent development of the research on three genes selected for by malaria are reported and discussed. Discrimination between beta and non beta thalassemia (T h) has been made, and some anomalies of the mendel ian segregation encountered in previous surveys have been corrected. The advantage of the presence of several genes controlling essentially the same character (i. e. thalassemia) is discussed. A possible mechanism underlying the protection offered by the sickle cell gene (S) against malarial infection has been suggested by recent investigations. The fact that G6P D deficient...