Age at marriage affects the size of completed family and the age pattern of childbearing. Much of the speculation on the effect of postponement of marriage on population growth has been in terms of the probable magnitude of the first factor, and comparatively little attention has been directed to the second. Birth and growth rates are compared in populations with different age patterns of childbearing. In high fertility populations differences in average age at childbearing can account for differences in the stable rate of population growth to an extent equivalent to 20% difference in fertility, even if the completed family size is identical in each childbearing pattern. This suggest that postponement of marriage can be an imporant component of population control, even if it is not accompanied by a reduction in family size. This has significant implications in countries currently characterized by high fertility and early marriages.