Members of Neotyphodium endophytic fungi infecting Lolium perenne L. and Lolium arundinaceum Darb. alter the synthesis of several metabolites. In this study we determined the antioxidative capacity of phenolic compounds from L. perenne and L. arundinaceum infected with Neotyphodium lolii (Latch, Christensen et Samuels) and Neotyphodium coenophialum (Morgan-Jones et Gams) Glenn, Bacon et Hanlin, respectively. The antioxidant capacity was determined by measuring the scavenging capacity of aqueous methanolic extracts to the free-radical DPPH (2,2-diphenyl-1-picrylhydrazyl). L. perenne infected with 'wild-type' strain endophyte showed the highest scavenging capacity, whereas endophyte-free showed the least. Those infected with the 'novel' strains AR1 and AR37 showed intermediate capacities. L. arundinaceum infected with the 'novel' strain AR542 showed a lower scavenging capacity compared with endophyte-free counterparts, regardless of the L. arundinaceum germplasm. The endophyte-free Mediterranean and ContinentalL. arundinaceum showed a higher capacity to scavenge DPPH when compared with the endophyte-infected Mediterranean and Continental L. arundinaceum. These results suggest that the endophytic fungi alter the antioxidative capacity of the grasses.