Endophytic fungi may reportedly improve summer persistence in tall fescue (Festuca arundinacea Schreb.). The objective of this study was assessing whether endophytes contributed to better persistence in 2 climatically contrasting Italian locations (Sanluri, Mediterranean climate, 382 mm average rainfall; Lodi, subcontinental climate, 802 mm average rainfall). Twelve populations from Sardinia were evaluated for 4 years in each site with or without nitrogen application. The populations hosted either of 2 endophyte forms (long-conidia, Neotyphodium coenophialum; short-conidia, FaTG-2 group) and belonged to the European race of fescue (hosting N. coenophialum) or the Mediterranean race (hosting FaTG-2). Three European-race commercial varieties (hosting N. coenophialum) were included as controls. The evaluated material was present both in the endophyte-infected and the endophyte-free (after chemical treatment) status. Stand persistence was recorded at the end of each year. The effect of the endophyte presence on persistence was nil in the Mediterranean site and slightly positive in the subcontinental location. Populations of the 2 geographic races had contrasting behaviour in the 2 sites irrespective of their endophyte status. The Mediterranean-race populations persisted well in the Mediterranean environment but not in the subcontinental one, and the reverse occurred for the European-race germplasm (including the controls). The results suggest that Mediterranean conditions may be too extreme for any enhancement of persistence to be solely provided by the endophyte, and highlight the overwhelming importance of the physiological adaptation of the grass germplasm to target environment.