Only gametocytes, the sexual forms of Plasmodium spp. parasites, can be transmitted to mosquitoes. The factors that control sexual development are incompletely understood. Marti and colleagues now identify lysophosphatidylcholine as a component in human serum that inhibits sexual development of Plasmodium falciparum. The parasite used this phospholipid for its choline and fatty acid metabolism, and its depletion increased the level of gametocytogenesis and induced a transcriptional response in metabolic, cell cycle and differentiation pathways. It has been previously shown that patients with malaria have low lysophosphatidylcholine levels. The authors conclude that parasite phospholipid consumption and inflammatory host responses decrease lysophosphatidylcholine levels both systemically and in certain tissues, which acts as a signal that induces sexual development, for example, at sites of vascular sequestration.