Blends of a Nynas 100 penetration-grade bitumen with a cis-polybutadiene, a butyl rubber, three polyisobutylenes of different molecular weights, a chlorinatedpolyethylene, polychloroprene in latex form, and a polyurethane rubber (scrap Lycra) were prepared using a Z-blade masticator mixer at a temperature of about 180°C. The blends contained between 10 and 40 pph (i.e., 9 and 29%) by weight of rubber. They were characterized by fluorescence optical microscopy, differential scanning calorimetry, and dynamic mechanical thermal analysis. The bitumen-rich phases provided the matrix in most of these systems, polymer-rich extensive phases being formed with butyl rubber, and low-and moderate-molecular-weight poly(isobutylenes) when the proportion rose above 30 pph, and for the poly(cis-butadiene) and chlorinated polyethylene system only when the proportion rose above 40 pph, according to the tan ␦ plots. Only glass transitions were associated with polymer-rich phases, and there were some melting transitions from paraffinic wax components ejected from the bitumen-rich phases. Below room temperature the modulus of blends of polybutadiene, chlorinated polyethylene, and the polyurethane rubber were similar to that of the bitumen; but those of the other polymers were stiffer by a factor of 50, perhaps because of a rearrangement of the asphaltenes. The softer blends, particularly the first two named above, had loss processes (with tan ␦ Ͼ 0.5) ranging over 200°C or more.