There are many couples who fail to conceive despite the absence of any apparent reasons, which remain undiscovered during complete infertility investigation or even after necessary treatment intervention. Such a condition may be termed as unexplained infertility. Criteria may include normal history and physical examination, adequate and appropriate coital frequency, three normal semen analysis, regular monthly cycles with a luteal phase of 12 days, adequate cervical mucus and normal post-coital test, normal hormone assay and tubal patency (hysterosalphingogram). The reported overall prevalence of unexplained infertility ranges from 6% to 27%. Male factors contribute significantly to unexplained infertility.

Male infertility of unknown origin is a condition in which fertility impairment occurs spontaneously or due to an obscure or unknown cause. It includes two categories, unexplained male infertility and idiopathic male infertility. The dividing line between them is semen analysis, which is normal in the unexplained category and abnormal in idiopathic infertility.

During the past couple of decades, several new methods for the assessment of human sperm function have been introduced. These relatively newer technologies have helped detect several defects at various stages of sequential events taking place in human fertilization in patients with otherwise unexplained infertility (UNFPA, 2002). After ruling out female infertility factors, erectile problems and coital factors, modern andrology may help to analyze the unexplained male fertility problem on the basis of cellular and sub cellular mechanisms. Furthermore, this analysis may lead to the selection of proper treatment options fitting the needs of patients with unexplained infertility (Agarwal et al., 2011) and failed IVF attempts.