Thermal degradation and thermo-oxidative degradation of natural rubber were observed by heating at 150-250 ํC for 2-8 hours. After thermal treatments molecular weight reduction percentage volatile matters, percentage acetone extract, and initial rate of degradation at 2 hours were determined. The results indicated an increase in percentage volatile matter and initial rate of degradation iwth temperature, heating time and concentration of sodium perborate. On a contrary, molecular weight distribution decreased with an increase in temperature and heating time. However, the data were inconclusive of how the concentration of sodium perborate effected the molecular weight distribution. The percentage acetone extract decreased when temperature and heating time increased. When heating at 350 ํC, 1.67 phr sodium perborate for 4 hours under atmospheric pressure, natural rubber with original average molecular weight of 1,000,000 was thermally cracked into lower molecular weight organic fractions. The fractions were collected, distilled and the composition of light distillate (b.p. 120-270 ํC) were identified by a GC-MS. The result showed a major component of molecular weight 136 which matched isomers of limonene.