In Japan, family size and reproductive health are important issues with the trend that women have been bearing fewer babies. In addition to the smaller number of children, Japanese are enjoying the longest average life spans in the world. The combined trends of a shrinking birthrate and an increasing number of elderly people have now become a serious issue. Recently, Japan's total population is believed to have shifted to a pattern of gradual and natural population decrease. The burdens of both child-bearing and caring for the elderly have been seriously concerned by Japanese women. Women tend not to be interested in getting married and having a baby because of heavy burden that mostly women have to suffer. Young reproductive-aged women often say that “Why do I have to get married, since I am happy with appropriate income and respected work?” They don't find children or family attractive. According to the Ministry of Health, Labour and Welfare, Japan's 2003 total fertility rate (average number of children each woman has in her lifetime) was 1.29, the lowest ever. The psychological impact of this further deepening of the birth dearth on Japanese society has been called the "1.29 Shock." Although the rate was also 1.29 in 2008, the actual number of births was only 1.12 million, well below the 3.00 million a year earlier. Recent studies show that the decline in the birthrate is caused 70% by an increase in the unmarried population and 30% by an increase in the number of married couples with no or only one child. (A survey conducted in 2000 found that 44% of women between age 25 and 29 were unmarried.) In addition, as having a baby at a later age become more common, gynecological diseases such as uterine leiomyoma, ovarian tumor and endometriosis affect the reproductive health and well-being of fertility. The specific aims of this study by conducting empirical studies of the US-Japan comparisons are: 1. To determine if traditional gender role adversely associated with the declining number of birth. 2. To determine if nation's declining birthrate can be reduced by the alleviation of a certain amount of gender differences.　　 In this study, we will use samples from major national representative surveys in US and Japan including information pertaining socioeconomic and health variables. As a main statistical method, we will use a multilevel analysis which can validly model the relationships between variables in different levels such as individual (gender and health), region, income, occupation and education (inequality), and country (social characteristics), health outcomes (perceived health, health risk behaviors, birthrates, mortality, morbidity especially on gynecological diseases, and fertility). By the comparisons between the US and Japan, we can figure out the effects of traditional gender role under the consideration of the differences in social characteristics such as culture, with or without immigration and type of social systems. We believe this will help solve the low birthrate problem in industrialized countries including the United States and Japan.