The effects of the maturation and storage of naturally coagulated latex, generally termed cuplumps, on some bulk rheological properties and on parameters characterizing the macromolecular chain length were investigated for natural rubbers of different clonal typologies. The sensitivity of the clonal material to the degradative effects of cuplump maturation increased with the level of tree energetic metabolism, with the most metabolically active plant materials (e.g., PB 235) being most sensitive, whereas the less active clone PB 217 was less sensitive. A definite relationshipevolves between Hevea tree metabolism and the stability of the structure of the biosynthesized rubber. The results presented here highlight at a macromolecular level the effects of maturation previously demonstrated on bulk processing parameters. © 2002 Wiley Periodicals Inc