Malaria infections in children often present dificulties in diagnosis and chemotherapy. Here we describe three cases of malaria with several considerations about the diagnosis, course of infection and post-treatment evolution. The first case was a 2 month old girl with a severe malnutrition and a post-transfusional Plasmodium vivax infection. Three different regimens of chloroquine were required to clear the infection. The second case was a 25 day-old boy who developed a Plasmodium vivax infection and methahemoglobinemia after treatment with primaquine. The last patient was a 8 year-old boy in fected with a chloroquine-resistent Plasmodium folciparum. After radical treatment with sulfadoxine-pyrimethamine and due to the presence of circualting gametocytes the patient received at the hospital 4 different therapeutic schemes including 10 days of I.V. quinine, sulfadoxine-pyrimethamine and trimethorpim-sulfamethoxazol.