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The objectives of the present study were to evaluate sideoats grama [Bouteloua curtipendula (Michx.) Torr.] populations, to set an ex situ plot, and to asses morphological diversity. From 2000 to 2003, 577 sideoats grama populations were collected in 13 Mexican States. In 177 established ecotypes, the following plant morphologic attributes were assessed: vigour, regrowth, forage texture, dry matter production potential, phenology, seed production potential, leaf density, tiller type and leaf:stem ratio. Variables were analysed through principal component analysis (PCA) using the PRINCOMP procedure. The first three components explained 62.9 % of the total observed variation. Principal component one (PC1) included characteristics related with growth and explained 36.4 % of variation; vigour, leaf density, and leaf:stem ratio were the most important variables. The PC2 included characteristics related with propagation and explained 15.1 % of variation; seed potential and tiller type were important variables. The PC3 explained 11.4 % of variation; forage texture and phenology were the most important variables. The PC1 and PC2 revealed the existence of six different groups. This dispersion reflects a wide morphological and genetic variation in this species; it was observed that this dispersion is not systematic, since it is possible to establish groups based on physiographic adaptation of ecotypes instead of locality or place of origin. It can be concluded that this variation is important while selecting the best forage characteristics in order to set up a genetic improvement program. [ABSTRACT FROM AUTHOR]