Chapter 2 analyses sociological and psychological research pertaining to same-sex parenting. This chapter builds onas it uses the relevant research to guide the application of the best interests principle. This research is used to inform the demands of the principle and to reduce the indeterminacy and subjectivity of decision-making as it relates to the children of gay and lesbian families. Existing sociological and psychological studies are assessed to determine whether children’s best interests can be served by same-sex parents and, consequently, whether legal recognition of these family relationships is desirable. This approach is also used to assess the application of specific laws in terms of their impact on the best interests of the child.