Background : The biting behaviour of mosquitoes is crucial for the transmission of malaria parasites. This studyfocuses on the feeding behaviour ofCulex pipiensmosquitoes with regard to the infection status by the avianmalaria parasitePlasmodium relictum(lineage SGS1). Methods : Uninfected and sporozoite-infected mosquitoes were provided with a choice between an uninfectedbird and a bird undergoing a chronicP. relictuminfection. Mosquito choice is assessed by microsatellite typing ofthe ingested blood. Results : Chronically infected birds are more attractive to mosquitoes. This choice is not altered by the infectionstatus of the mosquitoes: both infected and uninfected mosquitoes have similar host choice behaviours and aremore attracted towards infected birds. Conclusions : These results support some, but not all predictions derived from the hypothesis that malaria parasitescan manipulate the behaviour of their mosquito vectors to enhance their transmission. The possible mechanismsdriving this manipulation, the evolutionary dynamics leading to the modification of the biting behaviour ofmosquitoes by Plasmodium sp.as well as the implications for malaria epidemiology are discussed.