A decrease in milk production on dairy farms may result in economic losses in the majority of cases. Veterinary herd health and production control programmes should deal with the prevention of these losses. Moreover, in the event of a decrease in milk production, efforts should be made to trace the possible cause, and corrective measures should be taken if required. The Herd Standard Cow (HSC) production is an important parameter in both production and farm management in the Netherlands. In the present paper, a model for the analysis of variations in the HSC is introduced. It concludes the steps to be taken by the practitioner to trace the causes of these variations.