The evaluation and management of the infertile man have evolved considerably because of the development of new methodologies associated with procedures for in vitro fertilization (IVF), particularly intracytoplasmic sperm injection (ICSI), and an increase in our understanding of the genetics of sperm function.1 Nevertheless, the physician is often confronted with a patient in whom the diagnosis of “unexplained infertility” is the most appropriate description of his condition. The treatment for this has remained mostly empirical and somewhat controversial because of the paucity of effective medical therapies and the expense of procedures such as IVF with ICSI.

The treatment regimen for an infertile man requires a secure diagnostic foundation to allow appropriate selection from potential therapies. In the past, there were few measures of sperm function in the laboratory.2,3 Historically, semen analysis has been used to estimate fertility potential in men.4 However, errors in interpreting the semen analysis occur frequently because such measures do not directly assess sperm function or define what constitutes the “minimally adequate ejaculate.” Moreover, there is variability in semen quality among different specimens, and there are temporal changes in sperm output and semen quality. The consideration of the reproductive potential of the sexual partner is equally important, and the evaluation of a potentially infertile man necessitates a thorough gynecologic review of the sexual partner to recognize any coexisting reproductive dysfunction.