['In this study, the influence of anthropometric and training parameters on race performance in ultra-endurance runners in a 24-h run was investigated.', 'Descriptive field study.', '24-h run in Basel 2007.', '15 male Caucasian ultra-runners (mean (SD) 46.7 (5.8 years), 71.1 (6.8 kg), 1.76 (0.07 m), body mass index 23.1 (1.84 kg/m(2))).', 'None.', 'Age, body mass, body height, length of lower limbs, skin-fold thicknesses, circumference of extremities, skeletal muscle mass, body mass, percentage of body fat, and training volume in 15 successful finishers were determined to correlate anthropometric and training parameters with race performance.', 'No significant association (p>0.05) was found between the reached distance and the anthropometric properties. There was also no significant association between the reached distance with the weekly training hours, running years, the number of finished marathons and the number of finished 24-h runs. The reached distance was significantly (p<0.05) positively correlated with the personal best marathon performance (r(2) = 0.40) and the personal best 24-h run distance (r(2) = 0.58). Furthermore, the personal best marathon performance was significantly and positively correlated (p<0.01) with the best personal 24-h run distance (r(2) = 0.76).'] Is personal best marathon performance associated with performance in a 24-h run and not anthropometry or training volume?