This study examined the psychological well- being of fathers and father-child relationships in families with a 7-year-old child conceived by donor insemination. Twenty-four donor insemination families and comparison groups of 25 egg donation and 32 unassisted-conception families were assessed using a standardized interview and questionnaires administered to the father, and father-child dyads participated in an observational assessment of father-child interaction. On the basis of perspectives from Parental Investment Theory and stress- related models, it was expected that donor insemination fathers would show raised levels of psychological problems and a poorer quality of parenting and have more conflictual relationships with their children than genetically related fathers in egg donation and unassisted- conception families. These hypotheses were not supported by the findings. Instead, it seems that commitment to parenthood may be more important than genetic relatedness for positive father-child relationships.Key Words: family interaction, father-child relations, fatherhood, fertility/family planning/infertility, parenting styles.Fathers are generally viewed as integral to positive family functioning, with children of highly involved fathers found to perform better at school and to have higher levels of psychological adjustment, social competence, and empathy than children whose fathers are less involved (Fagan & Iglesias, 1999; Flouri & Buchanan, 2002; Lamb, 2010; Parke, 2002). Research on the mechanisms through which fathering influences child development has shown that fathers influence their children in ways similar to mothers, with sensitive yet authoritative parenting found to be positively associated with children's socioemotional and cognitive development (Bronte-Tinkew, Moore, & Carrano, 2006; Lamb, 2012; Lamb & Lewis, 2010; Marsiglio, Day, & Lamb, 2000). Fathers in families created by donor insemination differ from fathers in unassisted-conception families in that they lack a genetic link with their children, raising concerns that this may interfere with the development of a positive relationship between them. It has been suggested that, in comparison to biological fathers in unassisted-conception families, donor insemination fathers may be more distant from and less warm toward their children (Baran & Pannor, 1993; Burns, 1987; Warnock, 1984) and may lack a sense of entitlement in their role as fathers (Cordray, 1999; Turner & Cole, 2000) in a way similar to stepfathers, who tend to disengage themselves from disciplinarian roles (Amato & Sobolewski, 2004; Hetherington & Stanley-Hagan, 2002). With almost 500 children currently being born each year in the United Kingdom through donor insemination (Human Fertilization and Embryology Authority, 2010), and an estimated 30,000 to 60,000 children born each year through donor insemination in the United States (Evan, 2009), it is important that these concerns are addressed.Evolutionary psychologists have framed these concerns in terms of Parental Investment Theory (Fox & Bruce, 2001), which explains differential parental investment in offspring in terms of reproductive survival such that parents will be more inclined to allocate important resources (e.g., time, caregiving, financial aid) to offspring with whom they share a genetic connection (Daly & Wilson, 1996, 1998; Hamilton, Cheng, & Powell, 2007). This view is based in part on the finding that stepfathers offer less direct care, engagement, financial aid, and playtime to their stepchildren than do biological fathers (Anderson, Kaplan, Lam, & Lancaster, 1999; Hofferth, 2003; Zvoch, 1999). Thus, from an evolutionary psychology perspective, donor insemination fathers may similarly be expected to show less positive relationships with their children in comparison to genetically related fathers.It has also been suggested that the stress associated with the experience of infertility and its treatment may have an adverse impact on parents' psychological well-being and may interfere with adjustment to parenthood when a long-awaited child eventually arrives (Burns, 1990; Daniels, 2005). …