Leaf length in perennial ryegrass meadows is a limiting factor for feeding grazing cows. In spite of the phenotypic selection efficiency to improve this trait, synthetic varieties hamper fixing favourable alleles. Our aim was to detect QTLs of vegetative plant height which is highly correlated to leaf length in order to start Molecular Assisted Selection (MAS). Two hundred plants from a cross between two elite plants were used to build a genetic map for each parent with 39 SSR and 47 AFLP markers. The maps consisted of seven linkage groups for both parents, with a length of 408 cM and 548 cM. Plant height was measured in a nursery on spaced plants during spring 2008. Using the Composite Interval Mapping method, we detected two QTLs of plant height in the parent RA958 B on linkage group 2 and 5. The one on LG2 co-localized with a QTL of earliness in vegetative growth after winter explaining 21% of variance. Moreover, two QTLs of plant growth rate were found on linkage groups 4 (RA958 F) and 7 (RA958 B), each of them explaining 11% of variance.