Recent medical literature has quite extensively addressed the use of various terminologies within the field of reproductive medicine. This discussion has, however, so far overlooked the fact that one of the most frequently made diagnosis, so-called unexplained infertility (UI), not only didactically but, even more importantly, clinically, appears unsustainable as an independent diagnosis. The arguments in support of such a contention are manifold. The diagnosis of UI is highly subjective. It is dependent on which diagnostic tests have been performed (or have been omitted) and at what level of quality. Paradoxically, a diagnosis of UI will, therefore, be more often reached if the diagnostic workup is incomplete or of poor quality. Supported by evidence from the literature, the argument is made that the conditions, most frequently misdiagnosed as UI, are endometriosis, tubal infertility (especially distal and peritubal disease), premature ovarian ageing and immunological infertility. Because of the obvious unreliability of a diagnosis of UI and the widely reported unevenness in diagnostic criteria, we recommend the abandonment of UI as a formal infertility diagnosis. Better efforts to reach infertility diagnoses more accurately should improve the diagnostic accuracy of hitherto frequently missed diagnoses, which often falsely have led to a diagnosis of UI.