OBJECTIVE: This paper examines to analyze what determines the demand for vaccination in the elderly as a high risk group. Then, by using the estimation results, this paper evaluate how the law recommendation and/or subsidy affect their demand. METHOD: Original data were obtained from two surveys to the elders living with decendants and the elders living without decendants , conducted by the author. The survey contains the information about the elders, the household, experience of influenza during the last season and immunization during and hypothetical questionare about immunization for Conjoint Analysis. The three estimations are performed for actual behavior; Conjoint Analysis and Joint Estimation which combine the first two estimation. RESULT: Among estimation results, cost, number of immunization, immunization in night or weekend, and law recommendation heavily affect their demand. Experience of influenza and immuzation in the last season are the most important determinants. Moreover, the superior of the Joint Estimation is confirmed. CONCLUSION: The estimation results imply that about 8.9 million elders will demand for vaccination if there is no cost and if there is a law recommendation. Conversely, it will reduce to 3.2 million if cost is 6000 yen (about $50 US dollars) and without law recommendation. The change from no cost to just 500 yen (about $4 US dollars) depresses the demand by 1.6 million elders. Law recommendation alone can push up 2.0 million elders.