Abstract: The present study highlights the potential of using lactate dehydrogenase (LDH, EC. 1.1.1.27) and aldehyde oxidase (AO, E.C.1.2.3.1.) activities and level of lipid peroxidation (LPO) in RBC as indices in monitoring the severity of P. falciparum malaria infections. Two hundred and forty one male patients from two major hospitals in Benin-City, Nigeria, with a history of malaria and confirmed to be infected with the P. falciparum malaria parasites by microscopic examination of Giemsa-stained thin blood slides were chosen for the study. These patients who fell within the 18-40 year age group were further grouped into low, moderate and high parasitemia based on the parasite density. A control group of healthy male adults in the same age range with the patients were also used for the study. Erythrocyte obtained from venous blood collected in heparinized tube after several centrifugations and appropriate washings with specified buffer solutions were assayed. The level of LPO in Infected Red Blood Cells (IRBC) was significantly higher (p<0.05) as compared to control with the level increasing with severity of malaria infection. Conversely, the LDH activity of IRBC was significantly (p<0.05) decreased relative to control and the decrease was also in the order of severity of the infection. However, no significant difference was observed in the AO activity in the different experimental groups. A significant (p<0.0001) negative correlation (r = - 0.9516) was observed between LDH activity and level of LPO. The results obtained suggest that LDH and LPO can be utilised as markers of malaria severity.