By using a dynamic micro-simulation model named INAHSIM, we conducted a population-household projection in Japan for the period of 2015 to 2070. Due to rapid aging of the population, the distribution of the elderly (65 years old or older) by living arrangements has a profound impact on the social system. Especially, the choice of the elderly among a) living in one-person households, b) co-residing with child households, and c) living in institutions, are crucial indicators for the future social burden of the elderly in Japan. In this paper, we projected the number and proportion of the elderly by living arrangement in future years. Trends of those elderly who have little relatives, therefore having high risk of dying in solitude, were also featured.Keywords: dynamic micro-simulation, population-household projection, living arrangements of the elderly, co-residing with a child, institution rate, solitary rate INAHSIM is a dynamic micro-simulation model, which was first developed in 1984-85 in Japan (Note 1). From the INAHSIM model, we can obtain a population-household projection in a coherent manner as well as dynamic statistics which are difficult to obtain from static surveys or macro simulation (Fukawa, 2012). As an example of such output, we prepared an index named solitary rate of the elderly.In this paper, basic features of the INAHSIM 2018 Simulation were described in Section 2, and results about living