The curing of unsaturated polyesters in the presence of organic and inorganic Γllers was studied by rheology and di β erential scanning calorimetry (DSC). A commercial resin was used as unsaturated polyester and pressed olive stones, which are an agricultural by-product, talc and quartz in di β erent concentrations were used as Γllers. The viscosity versus time at di β erent temperatures was recorded and the gel time (G) was determined by the sharp increase of viscosity, which involves the beginning of the crosslinking reaction. DSC records the exothermic peak due to the double bonds breaking to give crosslinked macromolecules. The results of both methods were treated kinetically. The activation energy and the pre-exponential factor A@ from the rheological method E v remained almost constant in the case of talc and quartz compared with the neat unsaturated polyester. With pressed olive stones as Γller, both parameters increased. On the other hand, the DSC results for the resins with inorganic and organic Γllers showed a decreased activation energy and frequency factor E a, D compared with the neat unsaturated polyester, whose activation energy k o, D E a, D and frequency factor were calculated to be 23.5 kcal mol~1 and k o, D 9.5 ] 109 s~1, respectively. The order of reaction was calculated to be close to 1. The olive stones inΓuenced the curing reaction, acting as an auxiliary accelerator.