In tropical countries, roads built with asphalt layers must be made with bituminous mixtures containing asphalt that is reasonably stiff to increase resistance against permanent deformations, i.e., rutting. When the available asphalt is not stiff enough, an alternative is to modify it using Gilsonite. This article presents the laboratory results of tests performed on samples of Gilsonite-modified hot mix asphalts modified by wet and dry processes. Gilsonite increases the stiffness and improves the performance grade of a virgin binder at high temperatures of service. Additionally, Gilsonite-modified hot mix asphalts developed a greater strength and stiffness under monotonic and dynamic loading.