Wallace plasticity and the weight-average molar mass (Mw) were measured on natural rubber samples of different origins. A sigmoidal model describes the relations between Wallace plasticity and Mw (0.872 > r[puissance 2] > 0.992) for given families of samples. The families of samples analyzed differed through their clonal origin, collection method (cup lumps or latex), and type of processing (CV or non-CV). This study showed that two samples of natural rubber can be identical in terms of plasticity, but very different in terms of the average polyisoprene chain length or Mw.