Within Australia, a diverse range of social and legislative contexts may be seen to either widen or narrow the reproductive and parenting options available to differing groups of people. For lesbians and gay men, restrictions upon access to reproductive health services, and the perceived or actual challenges in starting a family, often result in these groups of people negotiating alternate ways of meeting their reproductive or parenting needs. One such alternate approach to conception involves the use of donor sperm by lesbian recipients. Such an approach brings with it a range of issues, dependent upon the beliefs and motivations of each party. Drawing upon quantified qualitative data collected through interviews with 30 Australian sperm donors, this paper explores how the sexuality and parent status of men, and the context in which they donate, are potentially associated with three variables: motivations to donate, understandings of the meanings of biology or genetic material, and the determination of children's best interests. The study found that gay men were less likely to be parents and more likely to donate in private arrangements. This was associated with being more likely overall to talk of being motivated by their relationship to the recipients; to have an interest in biology as a genetic legacy; and to believe that children should determine their own best interests. Heterosexual men were more likely to be parents and to donate anonymously to clinics. This was associated with being more likely overall to speak of their donation as an altruistic gift; and to see children's best interests as appropriately determined by adults. The paper concludes by outlining a model for understanding the differences between gay and heterosexual sperm donors that takes into account the impact of social contexts upon individual motivations and beliefs.