A randomized, controlled, open-label parallel-group, single-center study to determine biomarkers of exposure to 12 selected harmful and potentially harmful constituents (HPHC) in cigarette smoke and urinary excretion of mutagenic material in 72 male and female Korean subjects smoking Lark One cigarettes (1.0 mg tar, 0.1 mg nicotine, and 1.5 mg CO) at baseline. Subjects were randomized to continue smoking Lark One cigarettes, or switch to an Electrically Heated Cigarette Smoking System (EHCSS) and EHCSS-K3 cigarette (3 mg tar, 0.2 mg nicotine, and 0.6 mg CO), or to no-smoking. The mean decreases from baseline to Day 8 were statistically significant (all p< 0.05) for 10 of 12 HPHC in mainstream cigarette smoke including CO (the primary objective) in the EHCSS-K3 group (range: -1.5% to -74.2%). Exposure to the other determined HPHC was not significantly different. In the Lark One group, the mean exposure to 6 of 12 HPHC in cigarette smoke was significantly (all p< 0.05) decreased; however, exposure to CO was significantly increased. The largest mean reductions in biomarkers of exposure to HPHC occurred in smokers who switched to no-smoking (-3.4% to -98.9%). The mean excretion of mutagenic material was significantly decreased (p< 0.05) in the EHCSS-K3 and no-smoking groups (-31.8% and -45.3%, respectively), and increased in the Lark One group (+31.5%).