Objective: To verify at preseason the isokinetic analysis in professional field soccer athletes. Methods:We prospective evaluated isokinetic analysis tests in 30 professional athletes aged between 18 and 35 years in the Portuguese Association of Sports in the preseason for evaluation of knee flexors and extensors at speeds of 60 degrees per second and 300 degrees per second. Descriptive Statistics were used to describe the sample data and t-Test for comparisons of test results with BioEstat 5.3 software. Results:The peak torque adjusted for body mass at speeds of 60º/sec and 300º/sec was higher in the knee flexors on the dominant side of the athletes. Conclusion:The knee flexors on the dominant side were stronger in relation to the non-dominant side in the two velocities studied.