The objective of this study was to estimate the direct costs of gastrointestinal nematode and liver fluke infectionsin the Flemish dairy population. First of all, the population at risk, the prevalence of production-limiting infections,the effects on animal production, the monetary value of animal products and the frequency and cost of ananthelmintic treatment were defined through a study and interpretation of specialist literature. Secondly, these elementswere incorporated in a spreadsheet and the annual costs were assessed for each infection. The annual cost ofgastrointestinal nematode infections was estimated at € 10.719.909 or € 38 per adult cow. The annual cost of liverfluke infections was estimated at € 8.270.765 or € 30 per adult cow. These figures do not present the average costof an infected animal, but reflect the relative importance of the disease. The results of this study emphasize thevalue of incorporating both infections in animal health programs.