Research in our laboratory is devoted to the creation of grapevine varieties resistant to downy mildew by exploiting the resistance found in Muscadinia rotundifolia. In order to obtain a first view on early molecular processes underlying the resistant response, we tried to identify differences in the expression levels of genes constitutively expressed in grapevine leaves by comparing the transcriptional profiles of resistant and susceptible pools of non inoculated plants. Two different methods to isolate genes putatively involved in resistance or defence signalling to downy mildew have been chosen. First, a cDNA Subtractive library was constructed by Suppression Subtractive Hybridization (SSH) and led us to amplify 119 clones. Through differential screening by macro-array hybridization, 64 clones were identified as resistance specific. Second, a cDNA-AFLP analysis was performed and 122 differential bands between susceptible and resistant RNA pools were detected. Sequence analysis of the differential expressed fragments will be presented.