This work is concerned, in the main, with reproduction - for which marriage is not an essential prerequisite. Nevertheless, much of sexuality and the greater part of parenthood still subsist within the marital relationship. Sex and marriage are interdependent - indeed the definition of the latter depends on the former. After looking at the prerequisites for marriage and for making a marriage void, the author shows that the medico-legal interests of marriage relate to the mental health and the sex of the parties. The author also looks at various aspects of the sexual-familial relationship, including contraception, sterilization, abortion, protection of the foetus, foetal experimentation, the infertile husband, the infertile woman, defective neonates and infants, consent to treatment and research in children, the protection of young children and the killing of children within the family. Cases are used to highlight the legal aspects of these subjects.