Six different compounds were prepared by using CBR-1203 type of cis polybutadiene rubber and SBR-1502 type of styrene butadiene rubber in different proportions. keeping fixed the total rubber quantity specified in the standard testing recipe, and the rheological properties of the subject compounds were measured. Also, 27 different compounds were prepared with CBR-1203 type of synthetic rubber using furnace blacks having different structures (DBP absorption value) and surface areas (iodine adsorption value), classed as N-220, N-330, N-550, N-660 by ASTM, and furnace blacks having different structures but similar surface areas, classed N-326, N-330, N-347, by changing the standard testing recipe proportions. Physical and rheological tests were carried out and the results compared. (C) 2002 Elsevier Science Ltd. All rights reserved.