The infection of people with haemophilia by human immunodeficiency virus (HIV) through blood transfusions demonstrated the potential risks of infectious disease transmission by transfusions. The microorganisms that can be transmitted through transfusion include: hepatitis viruses B, C, D, and G, HIV, cytomegalovirus, human T lymphotrophic virus (HTLV I and II), Treponema pallidum, Brucella spp, Toxoplasma gondii, Plasmodium spp and trypanosoma cruzi. We estimated the prevalence of transfusion-transmissible HIV, hepatitis B and C viruses, syphilis, and Plasmodium falciparum infection in two groups of blood donors at Douala city over the period of 1995 -2004. Our results for the donors at Douala University show that at points during that period the seroprevalence of HIV ranged from 2.20% to 8.12%, for HBV from 6.10% to 16%, for HCV from 0.80% to 1.65% and for syphilis from 1.10 to 22.81%. For the blood bank of Laquintinie Hospital we observed the following prevalences: 7.89%, for HIV, 6.91% for HBV, 2.32%, for HCV, 7.90% for syphilis, and 12.82% for P. falciparum infection. These results highlight the need for continuous monitoring for safe blood transfusion.