Description: Reducing the incidence of mastitis is measure aimed at increasing the quality of milk and dairy products. Effective economic argument for mastitis losses could contribute to promoting the prevention of this disease. According to literature data and model calculations the aim was to: - highlight the incidence of mastitis in cow herds; - analyze production losses caused by mastitis; - generalize the obtained knowledge. Relevant literature data (A) and two published data sets (B1 and B2) were statistically analyzed by method of meta-analysis. In addition to the milk losses also next economically important indicators were observed: - PROCENT of infectious animals; - somatic cell count (SCC ) in milk; - the total count of microorganisms (TC M); - fat content (F); - protein content (P); - selected indicators of reproduction. Relationship between SCC and decrease in milk production showed correlation 0.775 (P<0.01). SCC increase by 100 103.ml-1 results in a decrease in production (regression coefficient b=1.82) by 2.0 PROCENT and vice versa. Relationship between SCC and lower milk production due to mastitis showed correlation 0.832(P<0.01).With the increase in SCC by 100 103.ml-1 the production is reduced by 51 kg per cow and lactation on average (b = 0.511). Relations between SCC and other indicators were significant (P<0.01; B1 and B2).SCC increasing by 10 103.ml-1 - resulted in reduction of F and P by 0.034 and 0.015 PROCENT and TC M increase by 1.77 103.mlЦ1 and decrease of F and P by 0.022 and 0.015 PROCENT and TC M increase by 0.26 103.ml-1