PALABRAS CLAVE: Guadua angustifolia kunth, propiedades mecanicas, microestructura. ABSTRACT: The Guadua angustifolia kunth GAK, was characterized in its microestructure, and founded the effect that this one presents in the resistance to flexion and to stress. The resistance to the flexion diminishes from the external to the internal layer, due to the reduction of the quantity of cells of fibers in this direction. The resistance to flexion values in the GAK diminishes with the presence of nodes due to the discontinuity of the fibers in this part of the material. The resistance to the stress as that of flexion diminishes of the external to the internal layer, aspect that relates that the quantity of the cells of fiber diminishes towards the internal layer.