Purpose: Lateral epicondylitis can cause limitations in upper extremity functions of patients due to the decrease in upper extremity muscle strength and endurance in patients. The aim of this study is to determine the effect of muscle strength and endurance on upper extremity functions in patients with lateral epicondylitis.Methods: Forty-five patients mean age: 47.60±3.22, 30 females, 15 male diagnosed with chronic lateral epicondylitis were included in the study. Upper extremity muscle endurance of the patients was evaluated with unsupported arm exercise test in 1st and 2nd diagonal pattern , upper extremity muscle strength of the patients was evaluated with Hand Held Dynamometer HHD , and upper extremity functions of the patients were evaluated with Lateral Epicondylitis Function Scale LEFS scores.Results: There was a moderate negative correlation between the unsupported arm exercise test endurance on the affected side and the LEFS scores of the patients with lateral epicondylitis p