The relationship between the force level of sustained isometric contraction and the time until two indices of muscular fatigue was compared for the right elbow flexors between 6 young women and 6 men. The strength of the maximal voluntary contraction (MVC) measured at the wrist with the elbow at right angle was significantly greater in men (267 +/- 35 N) than in women (163 +/- 23 N). Endurance tasks were performed at randomly assigned contraction levels of 5, 10, 15, 20, 30, 40, and 50% MVC. The relative force (F% MVC) or the absolute force (F N) versus the endurance time or the time of pain ("itai") appearance (T min) curves were fitted to the following equation: log T = a + b.log (F--k). The most fitted equations were determined for each individual and each sex group by the value in the coefficient of determination. When comparing the curves in terms of the relative force, the endurance time and pain appearance time were longer in women than in men, particularly at lower contraction levels. In terms of the absolute force, however, they were longer in men than in women, particularly at stronger contractions. At lower contraction levels, less than 70 N, some women were similar to some men in fatigability.