Plant endophytes are gaining more and more attention around the world. This article summarized the studies on endophytic fungi inhabited in various grasses grown in the world, especially focused on clavicipitaceous endophytes inhabited in cool-season grasses. Symptomatic Epichlo spp., occasionally produce stromata on the culm of the host, and asymptomatic Neotyphodium spp., usually never produce any symptoms, were regarded as epichlo endophytes. Fungal species in epichlo endophytes and their geographic distributions all over the world were discussed. Furthermore, recent achievements in investigations on grass endophytes native to China were summarized and prospects on grass endophyte survey in the world were also discussed. Finally, based on these information, a potential of new endophytes harbored within warm-season grasses grown in most areas of the world and cool-season grasses grown in South America and Asia was predicted. In conclusion, bioresources of grass endophytes and their biodiversity should be abundant worldwide, and grass endophytes are worth full for collecting attentions in biological sciences.