Understanding of the pathophysiology of defective spermatogenesis, spermatozoa, and germ cell function must be advanced so that appropriate rational treatment, such as gene therapy, can be developed. Despite the dramatic advances in ART, one ultimate goal must be to develop treatment so that the couple can conceive naturally. Because such treatment will not be possible in all cases, a complementary step will be the ability to induce the production of haploid, functionally competent germ cells that can be used for ART. The achievement of these goals will be based on advances in many other disciplines. Whatever the future holds, it promises to be exciting.