CIRAD is carrying out a project to breed maize for resistance to maize streak disease. Plant response to maize streak virus (MSV) infection has been assessed by artificial inoculation using a selected population of Cicadulina mbila in which 100% of the leaffloppers were able to transmit MSV. This was possible because transmission ability is subject to simple genetic control encoded by the sexual chromosome X This study aimed to understand the molecular and cellular mechanisms of MSV transmission through C. mbila. Two leafhopper populations, homozygous for the transmission trait and derived from the same parents, were selected, one population containing 100% transmitters, and one containing 100% non-transmitters . The retention time of the virus inthe leafhoppers after a 3-day acquisition period was assessed in each population and for a non-vector species, C. chinaï. The transmitters kept the virus throughout the experiment (21 days), the nontransmitters for I I days and C. chindf for less than 3 days. The involvement of a receptor on the brush border of the gut was investigated on gut sections, using purified MSV as a figand followed by immuno-enzymatic labelling. Labelling was obtained with transmitters and non-transmitters as well as with C. chinaY. Moreover, labelling was also obtained with a non-transmissible virus, the rice yellow mottle virus. These results are discussed in relation to the transmission specificity of MSV through C. mbila.