The intraerythrocytic form of the human malaria parasite Plasmodium falciparum relies on glycolysis for its energy requirements. In glycolysis, lactate is an end product. It is therefore known that lactate accumulates in in vitro culture; however, its influence on parasite growth remains unknown. Here we investigated the effect of lactate on the development of P. falciparum during in vitro culture under lactate supplementation in detail. Results revealed that lactate retarded parasite development and reduced the number of merozoites in the schizont stage. These findings suggest that lactate has the potential to affect parasite development. (C) 2014 Elsevier Ireland Ltd. All rights reserved.