The purpose of this study was to determine the reliability of an isokinetic test for ankle dorsiflexion fatigue on a Biodex dynamometer. Young (21 to 32 years), recreationally active men (n = 10) and women (n = 10) performed 50 concentric (60 • s−1) dorsiflexion contractions, on two different occasions. Total work (TW), losses in work (work fatigue; WF), as well as relative losses in peak torque, an example being "3-3" which compared the first three to last three repetitions, were measured. The intra-class correlation coefficients (ICC2,1) and coefficients of variation (CV), as well as the Bland-Altman plots and analyses showed that the variables using peak torque and TW were more reliable than WF, with WF having a CV of 11.3% and the best peak torque variable, 3-3, having a CV of 5.6%. In conclusion, ankle dorsiflexion fatigue can be reliably assessed on a Biodex dynamometer. Key words: ankle joint, skeletal muscle, reproducibility of results, muscle fatigue, physical endurance