1.As a result of a survey of 3,377 bloods and 3,005 spleens in the Medellín-Itagüi area of Antioquia, Colombia, 8 per cent of the bloods of school children, and 11 per cent of the bloods of persons examined from all age groups in their homes, had plasmodia, and 25 per cent and 28 per cent, respectively, of the spleens examined among the same groups were enlarged.
2.Plasmodium vivax was the only parasite which was encountered in significant numbers, although in a few bloods, P. falciparum was found.
3.Anopheles argyritarsis, Anopheles pseudopunctipennis, Anopheles eiseni, and Anopheles punctimacula were the only anophelines found in the area during 16 months of study.
4.Anopheles punctimacula was the only species which frequented human habitation, and also the only one found to be naturally infected.
5.It is of importance in the planning of control work that this species was found in breeding places far removed from wooded land, in urban water holes fully exposed to the sun.