Despite the fact that synthetic rubbers have become very competitive in the world rubber market, a demand for natural rubber in some applications remains appreciably high as a consequence of its superior elasticity, resilience, and heat-transfer properties. Offensive odor emitted from natural rubber products and from natural rubber raw material during drying, storage, mastification, and curing has been recognized as a long-standing, unsolved problem for natural rubber manufacturers and consumers. Low molecular weight volatile fatty acids were identified as major odorous components according to an indirect analysis of exhausted gas emitted from natural rubber factories.1–2 Systematic identification of odorous contents of different-graded solid natural rubber by gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS) by using headspace as a direct sampling technique later confirmed that low molecular weight volatile fatty acids are the major cause of offensive odor.