The C34T mutation in the gene encoding for the skeletal muscle-specific isoform of AMP deaminase (AMPD1) is a common mutation among Caucasians (i.e., one of five individuals) that can impair exercise capacity. The purpose of this study was twofold. First, we determined the frequency distribution of the C34T mutation in a group of toplevel Caucasian (Spanish) male endurance athletes (cyclists and runners, n = 104)). This group was compared with randomly selected Caucasian (Spanish) healthy (asymptomatic) non-athletes (n = 100). The second aim of this study was to compare common laboratory indices of endurance performance (maximal oxygen uptake (VO_2max) or ventilatory thresholds)) within the group of athletes depending on their C34T AMPD1 genotype. The frequency of the mutant T allele was lower (P<0.05) in the group of athletes (4.3%) compared to controls (8.5%). On the other hand, indices of endurance performance did not differ (P>0.05) between athletes carriers or non-carriers of the C34T mutation (e.g., VO_2max: 72.3 ± 4.6 ml^.kg^-1.min^-1 vs. 73.5 ± 5.9 ml^.kg^-1.min^-1, respectively). In conclusion, although the frequency distribution of the mutant T allele of the AMPD1 genotype is lower in Caucasian elite endurance athletes than in controls, the C34T mutation does not significantly impair endurance performance once the elite level status has been reached in sports.