The cross-country world championship is one of the best models to study characteristics needed to achieve top-level endurance athletic capacity. We report the genotype combination of a recent cross-country champion (12 km race) in polymorphisms of seven genes that are candidates to influence endurance phenotype traits (ACTN3, ACE, PPARGC1A, AMPD1, CKMM, GDF8 (myostatin) and HFE). His data were compared with those of eight other runners (world-class but not world champions). The only athlete with the genotype theoretically more suited to attaining world-class endurance running performance was the case study subject. A favourable genetic endowment, together with exceptional environmental factors (years of altitude living and training in this case), seems to be necessary to attain the highest possible level of running endurance performance.