Infertility is defined as the inability or failure to conceive within 12 months with regular sexual intercourse. In most Western countries, approximately 15% of couples are involuntarily infertile, and demographic studies show that about 5% of women have not had children after 5 years of marriage. While some, perhaps half, of these couples are actively practicing contraception, the others have chronic infertility. In the United Kingdom it has been estimated that 24% of women will consult a doctor about infertility at some stage during their lives.(8) While various surveys have put the frequency of male disorders causing infertility at about 25%, this is very much dependent on the definition of male and female infertility disorders and on the thoroughness of investigation.(7) It is most important to recognize that with the exception of cases in which there is an absolute barrier to fertility, combined factors in both partners are frequently operating. For example, there may be as many ollgospermic fertile men in the general community as there are oligospermic men who seek treatment for infertility, with the difference between the two groups being the relative fertility of their partners.