Despite the importance of forage grasses for livestock in Brazil, the amount of information available remains limited, especially for breeding purposes. The basic knowledge about any given species is fundamental to direct genetic improvement programs, helping in the selection of efficient strategies that will lead to a greater selection gain. Essential information includes reproduction mode and outcrossing rate, which help not only breeding programs but also germplasm conservation. Traditional methods employed to evaluate outcrossing rate use morphological analyzes of the flowers, greenhouse experiments and observation of pollinator behavior. However, the most rapid and efficient way to estimate outcrossing rate is to use genetic markers already analyzed in the progenies. Embrapa Gado de Leite coordinates the breeding program of Pennisetum and Cynodon, and basic information such as outcrossing rate are essential to assist in the management of these programs, giving supplementary support in choosing efficient methods for the selection of superior genotypes. Thus, this project aims to estimate the outcrossing rate in elephantgrass and Cynodon, using molecular markers. Three populations of P. purpureum and three populations of Cynodon belonging to the breeding programs conducted by Embrapa Cattle of Milk are used. At the time of the flowering of the species, seeds of 20 individuals are collected in each of the six populations under evaluation. Twenty individuals from each progeny are evaluated using ten microsatellite markers. These markers are selected based on the existing polymorphism between the parental genotypes. The information generated will contribute, in a relevant way, to help the breeding programs, besides contributing to the knowledge and preservation of the species studied.