Abstract: A mean fibril angle of Pinus massoniana is measured by means of. Polarized-light microscopy. Single cell walls of wood fibers are halffibers produced by maceration of microtomed wood tangential sections. The mean fibril angle of latewood tracheids is smaller than that in the earlywood tracheids, and the mean value of sapwood is larger than that in the heartwood too. The mean fibril angle measured by polarized-light microscopy agrees well with the values obtained by iodine staining and X-ray (002) diffraction. It shows that the technique for measuring fibril angle using polarized light is feasible.