This paper deals with the determination of the parameters of the constitutive law of a NR filled carbon black aggregates. The experimental technique involves an optical laser speckle extensometer. Digitalized images are recorded at successive states of deformation. The whole bidimensional field of inplane displacements is obtained by cross-correlations. Experimental data from tensile tests, pure shear tests and double-edge notched samples are presented. The experimental results have been compared with numerical simulations from the Rivlin constitutive equation into a finite element code.