Objective: Threshold of cost-effective analysis is thought to be £20,000-£30,000 in UK and $50,000-$100,000 in the US, however it is known that these values are not based on explicit scientific evidence. We measured WTP for one additional QALY gain to determine the threshold of cost-effectiveness analysis. Methods: We measured willingness to pay (WTP) for additional one year survival in perfect health status to determine threshold of incremental cost-effectiveness ratio (ICER) by the internet. The number of subjects is 1000 (500 male and 500 female in their 20s to 50s) in Japan, Republic of Korea (ROK), Australia and UK. We asked them four kinds of WTP, i.e., 1) WTP for their own additional QALY: (WTPsel); 2) WTP for their own additional QALY 5 years later: (WTP5sel); 3) WTP for their family's additional one QALY: (WTPfam); and 4) the amount they think society should pay for someone's additional one QALY: (WTPsoc). The double bound dichotomous choice was applied to this research analyzed by nonparametric Turnbull method. Results: The value of WTPsel is ¥5 million (Japan), ROK70 million Won, AUS$64,000 (Australia) and GBP23,000 (UK). Discount rate of outcome was calculated by comparing WTPsel with WTP5sel, and it is estimated to be 6.8% (Japan)?3.7% (ROK)?1.9% (Australia) and 2.8% (UK). The order of four kinds of WTP is WTP5sel Conclusion: Considering the value of WTPfam (¥6.4 million), we think the threshold of ICER should be determined to be ¥5 million to ¥6 million per QALY in Japan. This result also shows the threshold and discount rate adapted by NICE is reasonable. The difference of four WTP's order may represent cultural gap between Asia and Western world.