The popular and scientific debates about a possible decline in semen quality over the past decades are largely based on retrospective analyses of semen analysis data performed in the past. This article will argue that the conclusions from such analyses are significantly weakened because the methods of laboratory andrology have changed considerably since the 1950s. In the last 20–30 years, there have been significant developments in training and competence, increased emphasis on Quality Assurance (QA) and Quality Control (QC) as well as a major attempt at standardisation of technique through five successive editions of the World Health Organization (WHO) laboratory manuals. Interestingly, the only large prospective study carried out to date shows no change in sperm concentration over 15 years, being consistent with the idea that when laboratory methods are adequately controlled, no secular change in sperm counts are observed.

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