BACKGROUND: A study was undertaken to assess the components of biological variation of seminal parameters in healthy subjects. METHODS: Twenty donor candidates were included in a 10‐week follow‐up study. Within‐ and between‐subject biological variation, indices of individuality and heterogeneity, coefficient of reliability, critical differences, analytical goals and the lowest value observed with a P < 0.05 for vitality, progressive motility and morphology (34.4, 49.2 and 58.0% respectively) were lower than for concentration (77.8%). CONCLUSIONS: The study results showed that conventional reference values for seminal parameters have little diagnostic value because of their marked individuality, though seminal parameters can be useful for assessing differences in an individual’s serial results, in particular of progressive motility, morphology and vitality.