According to the literature, the incidence of clinical mastitis reaches on average around 30% of dairy cows per year, significantly higher occurrence is usually reported for subclinical mastitis. On amount of the economic loss caused by mastitis has a major share lower sale of milk due to reduced milk yield and milk exclusion of deliveries within the withdrawal period. At high variability (about 475 to 640 kg), an average loss is estimated at 565 kg milk per occurrence of one mastitis. Other causes of loss include higher culling of cows, the cost of cow treatment, higher labour consumption (about 1 to 4 hours of occurrence) during therapy of dairy cows, worse indicators of fertility, low quality of milk (low fat and usually proteins in milk, higher numbers of somatic cells), etc. The results of the analysis of milk quality in Czech and Bavarian laboratories confirmed significant relationships between the number of somatic cells and fat (r = -0.535 and -0.508), proteins (-0.439 and -0.469), and the total number microorganism (r = +0.510 and +0.630).