The aim of this work was to present an in vivo protocol to estimate the carrying angle of the elbow in full extension. Forty-four arms were measured by using an electrogoniometer to acquire 3-dimensional coordinates of the landmarks. An algorithm based on the Cardan decomposition method was used to compute the carrying angle and the flexion and pronation angles of the elbow. The mean carrying angle was 12.42 degrees +/- 4.06 degrees , in agreement with the literature and with values obtained by a standard goniometer (r = 0.46; P = .000). Our protocol provided excellent repeatability (interclass correlation coefficient [ICC] = 0.85), greater than a goniometer (ICC = 0.76), and a standard error of measurement of only 1.62 degrees . Flexion was a significant factor (P = .01) in carrying angle estimation. This study suggests that the carrying angle cannot be estimated independently by the flexion angle, even when measured in apparently full extension, and it could be useful in elbow disorders, such as fractures or epicondylar disease management and evaluation of elbow reconstruction.