Importance and control of chronic mastitis in dairy herds Summary: Cows with chronic mastitis represent an important economical factor for dairy farming, due to clinical mastitis cases, antibiotic use and milk losses in dairy farms. A systematic approach is needed to avoid futile therapies and insufficient results. This is possible by applying analysis and control concepts presented here which are based on actual scientific data. A prudent use of antibiotics in dairy cows relies not only on including cure rates in the decision-making, but also on evaluating whether the expected higher cure rates due to extended therapy durations will justify higher costs and whether there will not be any adverse effects due to the particular new infection rate of the herd in question.