Up to now, there are few economic analyses which construct models taking account of tobacco-associated diseases in Japan. OBJECTIVES: To develop markov-model including various tobacco-associated diseases to evaluate effects of nicotine-replacement therapy (NRT) and smoking cessation guidance therapy. METHODS: To identify various tobacco-associated diseases and markov transition probabilities, we organized a committee including expert physicians. With expert interview, we developed a markov-model. RESULTS: We identified 19 tobacco-associated diseases as major results from smoking, according to "Heatlth Risk Appraisal". The 19 diseases are as follows; 10 cancers - oropharyngeal cancer, esophageal cancer, gastric cancer, hepatic cancer, rectal cancer, pancreatic cancer, lung cancer, cervical cancer, renal cancer and bladder cancer; 4 cardiovascular diseases - hypertensive heart disease, ischemic heart disease, aneurysm and apoplexy; and 5 other diseases - pneumonia, chronic bronchitis, asthma, gastric ulcer and cirrhosis. Tobacco is thought to increase incidence rate of those 19 diseases. We constructed four node markov model, "Success (of smoking cessation)" "Failure" "Death" and "Sick". "Sick" node consists of 19 diseases. We also considered combination of major diseases. In order to avoid many branches, we settled transition probabilities of diseases as cumulative function of incidence of each disease. Main assumptions are as follows; i) Only one disease occurs during one cycle; ii) Risk of each disease increases as cumulative tobacco consumption; and iii) Smoking affects incidence rate of 19 diseases but does not affect mortality rate after those diseases. One cycle in markov chain is set to one year. For future cost-effectiveness analysis of smoking cessation therapy, we set cost as well as transition probability on each branch. CONCLUSIONS: We developed markov-model, including various tobacco-associated disease. In the future, we will take cost-effectiveness analysis to evaluate smoking cessation therapy using this model.