F. H. Comhaire Many diseases were, at the beginning, merely defined by the description of their clinical appearance. Next, the pathogenic mechanisms underlying the diseases were recognized. Since then, the proof of presence of the pathogenic agent or agents has been required to confirm the diagnosis. However, it sometimes happens that the pathogenic agent can be demonstrated without the disease being clinically evident. Confusion arising from this observation may cause endless, often purely emotional discussions between "believers" and "non-believers." Moreover, if the disease involves potential disturbance of male fertility, the problem is further obscured by the difficulty of defining man's fertility. Indeed, during the short history of andrology, the criteria for judging a man and his ejaculate as potentially fertile or infertile have repeatedly changed. Andrological "landmarks" in general do not hold up for long, and some scientists continue to set themselves the task of proving the "old" definitions invalid. Certainly, such developments are necessary to make science more exact and to improve medical care. However, while this research is being done, the male partners of barren marriages continue to seek advice and treatment. Common sense and an empirical approach in the handling of these cases may result in obviously encouraging results, which non-believers will ascribe to "witchcraft" and believers will see as confirmation of their opinions.

It is not surprising that so much investigation has been undertaken to establish the cause of childlessness, especially when the potentia coeundi of the male is not impaired. As long ago as 1957 the German Society for the Study of Fertility and Sterility was founded, embracing gynecology, andrology, and veterinary medicine. After its inception, meetings conducted in the spirit of its foundation were held every 2 years. This interdisciplinary, coordinated scientific work in the field of human reproduction achieved its value as a result of the stimuli provided by the permanent involvement of veterinary scientists. After about 20 years of activity, the Society adopted a highly differentiated pattern of work-directions in the field of human and veterinary medicine. Since 1976 annual meetings have been held on the topic of animal and human reproduction. These meetings have proved of great value, especially in the area of comparative medicine, and have led to excellent interdisciplinary associations. One of the most evident successes was the first extracorporal fertilization in humans with subsequent embryo transfer and full-term pregnancy. Gynecologists have found that in 40% of cases the cause of undesired childlessness rests with the male, and it is therefore no surprise that also in the field of andrology certain factors concerned with infertility have received great attention.