Abstract The distribution of different Epichloe species within eight natural populations of Lolium perenne was studied. In total, 40.2% of the asymptomatic plants were infected by Epichloe festucae var. lolii or by Epichloe typhina. Both species occurred in sympatry in seven grass populations, and some plants had dual infections by both taxa. No hybrid taxa such as Epichloe hybrida were detected. Epichloe festucae strains were classified into two morphotypes, M1 and M3, according to culture characters, both morphotypes occurred in sympatry in seven populations. Plants bearing stromata produced by Epichloe typhina were observed, but asymptomatic plants infected by this species also occurred in seven populations. The alkaloid profile of Lolium perenne plants was related to the morphotype of their infecting strains: most plants infected by M3-strains were characterized by lolitrem, and those with M1-strains contained either ergovaline or lolitrem. Plants infected by Epichloe typhina were characterized by high peramine content.