The ultrasonically devulcanized carbon black filled NR was mixed with virgin carbon black filled NR. The properties of the blends were studied and compared with those of the blends of fully cured ground NR and virgin NR. Curing characteristics of the blends indicated that an increase in the devulcanized NR content decreased the cure time and the scorch time. The tensile strength and elongation at break of the blends with ultrasonically devulcanized NR were much better than those of the blends with ground rubber. As the proportion of the virgin NR in the blends was increased, the mechanical properties progressively increased.