Various instruments and utensils used during milking as well as teat dip solutions were examined for contamination with coagulase-negative staphylococci (CNS). The goal of this study was to investigate the relationship between contaminated fomites and udder infection in dairy cows. A total of 344 cows from ten dairy farms with the highest rate of clinical mastitis among the farms serviced by the Ambulatory Clinic of the University of Zurich were included in the study. Each farm was visited five times. All lactating cows, with the exception of those undergoing antibiotic treatment, were examined immediately before milking using the California Mastitis Test (CMT). A milk sample was collected from positive quarters. Items used to clean the udder, which included wood wool, paper towels and disinfecting towels as well as the milker's hands and the teat dip cup were swabbed for bacteriological examination. Water samples, samples of teat dip and cleaning solutions were also collected and cultured. Our results demonstrate that cleaning and disinfecting solutions have the potential to transmit udder pathogens and cause clinical mastitis. The most common CNS isolated from quarter samples were S. saprophyticus, S. sciuri and S. chromogenes, and the most common CNS isolated from utensils, cleaning and disinfecting solutions were S. fleuretii, S. vitulus, S. equorum, S. sciuri, S. haemolyticus, S. succinus and S. saprophyticus.