Safety of Keum-Yeon-Cho (NosmoQ), a tobacco substitute composition, was evaluated in terms of acute- and 4 weeks repeated-inhalation toxicity, mutagenicity, and immunotoxicity using Balb/c mice. The air inside the inhalation chamber was collected and analyzed by GC-MS. In acute inhalation toxicity test, male and female mice were exposed to 40 Keum-Yeon-Cho cigarettes. The 50% lethal concentration (LC(50)) of NosmoQ was considered to be much higher than 40 cigarettes in both sexes. In 4-week repeated inhalation toxicity test, male and female mice were exposed for 6 h/day, 5 days/week for 4 weeks to 10 and 20 cigarettes per day, while control mice were exposed to filtered air. Our data indicated that no observed adverse effect level (NOAEL) of Keum-Yeon-Cho should be over 20 cigarettes per day. Results of Salmonella typhimurium reversion assay with/without histidine moiety, in vivo chromosomal aberration and in vivo micronucleus assays using mouse bone marrow cells revealed that Keum-Yeon-Cho has no mutagenicity. Evaluation of peripheral cellular immunity of mice treated with Keum-Yeon-Cho using in vitro lymphocyte proliferation assay showed no significant difference in mean stimulation index (SI) between mice exposed to Keum-Yeon-Cho and control mice. Mean CO concentrations and total particulate matter contents of 10 and 20 cigarettes were 21.1±1.23 and 40.7±1.21 ppm (mean±S.D., n=5), and 25.7±3.09 and 59.0±4.0 mg dry weight (mean±S.D., n=5), respectively. Although at negligible concentration (less than ppb level) several polycyclic aromatic hydrocarbons (PAHs) were also detected, these results indicate that NosmoQ has no toxic effect on mice.