BACKGROUND: Physical activity and a healthy diet may delay the aging process and ultra-endurance exercise is an extreme form of physical activity. Telomeres are protective DNA sequences located at the ends of eukaryotic chromosomes which shorten as we age. OBJECTIVE: The aim of this study was to investigate the relationships of lifetime physical activity and diet with salivary cell telomere length in current ultra-endurance exercisers (n = 49; %female = 37, age range 26–74 years). METHODS: Physical activity and dietary intake were measured using the Lifetime Physical Activity and Diet Questionnaire (LPADQ) and salivary cell telomere length was measured using quantitative polymerase chain reaction. RESULTS: In this group of current ultra-endurance exercisers there was no relationship between lifetime physical activity or diet (according to food category scores) and telomere length. In contrast to the expected age-related decrease in telomere length, there was no relationship between age and telomere length (95%confidence interval [CI]: –38.86, 14.54, p = 0.359) in this group of current ultra-endurance exercisers. CONCLUSIONS: The relationships of lifetime physical activity and diet with telomere length remain uncertain. It is possible that lifetime physical activity (including ultra-endurance exercise) and lifetime diet may independently, or in combination, contribute to a decrease in the rate of age-related telomere shortening in current ultra-endurance exercisers. ultra-endurance exercisers.