Management style and its association with bulk milk somatic cell count (SCC) and the incidence rate of clinical mastitis were studied in 300 Dutch dairy herds. Cluster analysis was used to identify groups of farmers who had similar management styles for the prevention of mastitis. Two groups of farmers could be differentiated. The management style of the first group of farmers was described as clean and accurate; the management style of the second group of farmers was described as quick and dirty. The relationship between clusters and the bulk milk SCC category was high. The relationship between clusters and incidence rate of clinical mastitis was weak. Compared with herds with a high (250,000 to 400,000 cells/ml) bulk milk SCC, herds with a low bulk milk SCC (< or = 150,000 cells/ml) were managed by farmers who were younger, had children with a higher education, and were more eager to invest. Farmers of herds with a low bulk milk SCC kept better records and were more familiar with each cow in their herds. The most striking difference between farmers of herds with low and high bulk milk SCC was that the first group worked precisely rather than fast; the latter group of farmers worked quickly rather than precisely. As a result, the farms with herds that had a low bulk milk SCC had better hygienic conditions than those farms with herds that had a high bulk milk SCC. We also discuss the implications for producer education with regard to udder health.