A Chinese herb has been added to tobacco in the belief that it might possibly prevent respiratory disease amongst its smokers. The composition of mainstream smoke from cigarettes with the herb added has been examined by solid-phase microextraction (SPME) sampling followed by GC, GC/MS analysis. The results showed that there were mainly 12 volatile and semi-volatile compounds in the herb, such as 4-morpholinepropanamine, 1-dodecene, ethopropazine and so on. There were 7 volatile and semi-volatile compounds in the mainstream cigarette smoke: 4-morpholinepropanamine, 1-propanone, 2-(diethylamino)-1-phenyl-, ethopropazine, 1,2-propanediamine, 2-propenoic acid, 3-phenyl-, methyl ester, 1-dodecene, 2,5-di-tert-butyl-4-methyl-phenol. Compared to the composition of the mainstream smoke of a cigarette without herb, the above 7 compounds were shown to be from herb but not from tobacco.