The authors make a brief revision about the duration of P. falciparum infection. Cases are mentioned in which the period lasted up to three years under a latent form. They refer to the risk that this fact represents in blood transfusions and finally relate three cases in which they believed that this fact had occurred and which could have serious consequences 1. By the possibility of spreading a strain of P. falciparum resistant to the different anti-malarials. 2. By the fact that the blood transfusions are generaíly made in patients with various debilitating conditions. 3. By the difficulty which technicians face when making a transfusion in detecting whether the parasite is resistant or not in asymptomatic cases. 4. By relatively significant diffusion of strains of resistant P. falciparum in various parts of the national territory