Abstract: To meet different requirements for mainstream smoke composition regulations,yields of total particulate matter(TPM),tar,nicotine,CO,tobacco specific nitrosamines(TSNAs),benzoapyrene(BaP),selected carbonyl compounds,phenol,HCN,NH₃ and selected volatile organic compounds(VOCs) in mainstream smoke were determined under ISO and Health Canada Intense(HCI) smoking regimens from 9 Virginia type cigarettes and 11 blended type cigarettes with tar levels ranged from 1.0 to 13.3 mg/cig.The results showed that:1) For single cigarette,the yields of the above components determined under HCI regimen were significantly higher than those under ISO regimen;the differences between ISO and HCI regimens were greater for low tar(≤6 mg/cig) cigarettes than those with high/moderate tar levels.2) On per unit nicotine basis,the yields of NNN,NNK,BaP and 1,3-butadiene determined under the two regimens were basically the same.The yields of CO,formaldehyde,crotonaldehyde and HCN in mainstream smoke of low tar cigarettes determined under HCI regimen were higher than those under ISO regimen,however those of high tar(>6 mg/cig) cigarettes were similar under the two regimens.3) On per unit tar basis,the yields of NNN,NNK,BaP and phenol in mainstream cigarette smoke determined under HCI regimen were slightly lower than those under ISO regimen;however the yields of CO,formaldehyde,crotonaldehyde and HCN in mainstream smoke of low tar cigarettes determined under HCI regimen were higher than those under ISO regimen.