In practice, paternity rulings are remarkably unimportant. With the exception of state welfare authorities pursuing mostly impoverished biological fathers, few paternity actions are brought, few mothers want to bring them and (even with state-sponsored pursuit) very few dollars get transferred to children as a result of them. In theory, however, paternity judgments are very and perniciously important because they keep alive the biological fatherhood ideal, an ideal that has never been reflected in law or fact and that is inconsistent with the emerging law of parental rights and responsibilities. This article challenges the biological fatherhood ideal and suggests that contract, or private bargaining between adults, both does and should play a more important role than biology in determining parenthood. A bargaining theory of parenthood is consistent with the traditional legal framework in which marriage defined paternity, parallel to the contractual doctrine governing most decisions in the reproductive technology area, and operative in many of the equitable parenthood cases vesting parental obligation in non-biologically related adults. It is also more reflective of the way parenthood is experienced by both parents and children. The article describes the ubiquity of parental bargaining and deal-making and goes on to evaluate the costs and benefits of a more comprehensive contractually-based paradigm for determining parenthood.