One of the most notable changes in the demography of family life in the late-20th century has been the increase in the proportion of cohabiting couples, and of those who become parents outside marriage. This is reflected in the legal powers of parents in respect of their children. Through questionnaires and interviews, this study examines issues around fatherhood and marriage, and in particular looks at the implications of the difference in legal status between married and unmarried fathers in this changing demography of family formation. It explores, from the father's perspective, why some parents choose to marry while others do not, and whether there are any differences between the two groups. It also looks at what fathers know about the legal implications of their choice, and what their views are on the difference in legal status between married and unmarried fathers. It looks, too, at what happens to unmarried fathers when they use the legal procedures currently available to acquire parental responsibility for their children. Finally, the author explores the possible legal implications for social policy of the findings.