The global environment is changing with increasing temperature, precipitation and CO2 concentration. Temperature is one of the major factors controlling seed germination and, in the context of climate change, breeding pasture species varieties adapted to new ranges of temperature could be necessary. Lolium perenne, Festuca arundinacea and Dactylis glomerata are the major perennial grasses species in temperate and Mediterranean regions. Furthermore, seed germination is a key trait for plant growth, affected by environmental conditions, particularly temperature and between different genotypes. The objective of this study was to analyse the genetic variability of three pasture grasses species in response to temperature during germination. Six natural populations of L. perenne, seven populations of F. arundinacea, and four populations of D. glomerata were evaluated. Four replicates of 100 seeds per population were tested for germination in the dark under eight constant temperature regimes, between 5 and 40˚C with 5˚C increments. Maximum germination percentage, initial time of germination and germination rates were estimated. Maximum germination percentage was observed that the responses for the species natural population showed signifi- cantly differences P<0.01. Results show that no germination at all was observed at 40˚C for any of the 17 natural grass populations. It was observed a differential sensitivity to our extreme treatments 5 and 35˚C. This study suggests that high genetic variability exists within species for response to temperature during germination. This variability could be exploited to breed new grass varieties adapted to the future climate.