Data from the National Longitudinal Survey of Youth reveal that approximately one-quarter of teenage mothers have a second child within 24 months of their first birth. The prevalence of closely spaced second births is greatest (31%) among young women whose first birth occurred prior to age 17. Teenage mothers' characteristics before the first birth (such as race or ethnicity and parents' level of education) and at the time of the first birth (such as years of schooling completed and whether their first birth was wanted) influence whether they have a rapid second birth. For example, those with more educated parents are less likely than others to have had a closely spaced second birth. In addition, young mothers who obtain additional schooling in the period after their first birth are less likely to have a closely spaced second birth, while those who marry are more likely to have a rapid second birth.