The researches are conducted in adults and children infected with the species P. falciparum and P. vivax. The results indicated that complement C4 level showed a marked fall during the course of acute malaria in both the children and adults infected with both species. A highly significant hypocomplementaemia was recorded (p < 0.01). Children infected with P. falciparum developed acute cerebral malaria, which was associated with marked hypocomplementaemia. A marked rise in C4 level was noticed on 10th day and it was found normal with reference to control, on 20th and 30th day. A considerable reduction in C4 complement was recorded in P. falciparum when compared to P. vivax.