Ageing does affect functional capacity through several changes at the peripheral muscle level that impair the muscles capacity to produce energy and generate force. The skeletal muscle-specific isoform of AMP deaminase (AMPD) plays an important regulatory role in muscle metabolism and in determining energy charge. Since nearly 20 % of the general Caucasian population is heterozygous (CT) for the most common C34T mutation of the gene (AMPD1) encoding for this enzyme, it would be worthwhile to study if such a condition further increases the effects of ageing. Twenty-one women (61 – 80 yrs) served as subjects, and depending on the results of previous genotyping, were assigned to a group with the C34T mutation (heterozygous; n = 4; mean ± SEM age: 71 ± 1 yrs) or with no mutation (n = 17; 68 ± 1 yrs). Several indices of maximal (peak oxygen uptake [V·O2peak], peak power output) and submaximal endurance performance (ventilatory threshold, mechanical efficiency) and functional tests (one-mile walk test and a specific test of lower-body functional performance [sit-stand test]) were compared between the two groups. No significant differences were found in exercise capacity between both groups, e. g. V·O2peak of 19.1 ± 1.0 vs. 20.1 ± 1.9 ml · kg-1 · min-1, V·O2 at the VT of 11.9 ± 0.6 vs. 12.9 ± 1.0 ml · kg-1 · min-1, or time to complete the one-mile walk test (951 ± 18 s vs. 962 ± 61 s) and sit-stand test (9.9 ± 0.2 vs. 9.2 ± 0.2) (no mutation vs. C34T mutation, respectively). Although more research is necessary, it seems that the C34T mutation of the AMPD1, at least in heterozygous individuals, does not affect functional capacity in the elderly.