Unlike many European countries, the US has no national paternity leave policy giving fathers the right to take paid time off work following the birth (or adoption) of a child. Despite this, prior research suggests that many fathers do take some time off work after a child is born. However, little is known about the determinants, circumstances or consequences of paternal leave-taking. In this paper, we use the first wave of data from the Early Childhood Longitudinal Study-Birth Cohort (ECLS-B), a new nationally representative panel study of over 10,000 children born in 2001, to examine these questions. We make use of ECLS-B questions asked directly of resident fathers pertaining to their participation in a range of child care-taking activities, as well as a rich set of measures about the father, mother and child. We find that the overwhelming majority of fathers take at least some leave at the birth of their child, but that the length of that leave varies a good deal. Our results also indicate that fathers who take longer leave are more involved in child care-taking activities nine months later.