Grenada is a small mountainous island with a population of about 80,000, the majority of whom are Negroes. All of the towns are situated on the coast, and the rural areas most heavily populated are not more than 2 miles back from the seashore. In 1929 Root and Andrews (1) in a malaria survey examined approximately 6,000 school children from all parts of the island and found a spleen index of 12.3 per cent and a parasite index of 5.1 per cent. Of the positive blood smears, 42.4 per cent were diagnosed as benign tertian, 43.8 per cent as malignant tertian, 11.2 per cent as quartan, and 2.6 per cent as mixed. The disease was found to be restricted almost entirely to the villages and the rural population on or very near the coast.