In this paper, we have traced changes in the patterns of first marriage in the United States for cohorts of men and women born in 1880 through 1965 and for the years from 1900 through 1983. There were striking changes in marriage rates associated with each of the world wars and with the depression of the 1930s. In addition to these short-term fluctuations, a long-term shift in marriage rates is observed over the period from after World War II until about 1970. By the end of the 1970s, however, marriage rates had returned to levels similar to those observed before the war. The basic similarity in the timing of changes in marriage rates across age levels and for both men and women, blacks and whites, is a striking characteristic of these marriage curves. There are also, however, important differences among these groups with respect to the magnitude and slopes of the shifts. The postwar marriage boom was strongest among the young (those under age 24) and among whites. Similarly, the declines in marriage rates observed in the 1970s were greatest among the young. The marriage rates for teenagers display trends that diverge in many respects from those of older persons. For example, the marriage rates of male teenagers did not show the "peaks" and "valley" associated with World War II for older age groups and female teenagers. Moreover, there is little sign of the postwar marriage boom among black teenagers of either sex. Indeed, the marriage rates of black teenagers began to decline soon after the war, and by the 1970s the marriage rates of both male and female black teenagers had fallen below those of their white counterparts, reversing the pattern that had existed through the first half of this century. During the twenty-five or so years of the postwar marriage boom, which we believe can be characterized best as a period phenomenon, there were trends-eddies within the mainstream-which are probably most easily interpreted as the consequence of a cohort effect.(ABSTRACT TRUNCATED AT 400 WORDS)