Since the middle of the 1970s the proportion single among those who are in the reproductive ages and the mean age at first marriage have been steadily rising in Japan. These phenomena have occurred without the concurrent increase in cohabitation and out-of-wedlock fertility which Western society hasexperienced since the middle of the 1960s. While these trends are more or less common to all social and economic segments of Japanese society, they are more conspicuous among women with higher levels of education. According to decomposition analysis, neither growing urban population, growing population concentration in the three largest metropolitan areas, nor rising employee-status or white-collar jobs have contributed to any great extent to such phenomena, while the rise in higher levels of education has somewhat done so. Through the review of surveys on attitudes and behavior related to marriage, it can be asserted that the rapid rise in women's social status has made them economically more independent, weakened the economic necessity of marriage for them and, at the same time, aroused their discontent with a family system based on a fixed division of labor by gender, or the breadwinner-homemaker system. This, in turn, has acted to raise the proportion single and the postponement of marriage.