The report summarizes the research of breeding to improve resistance to clinical mastitis in dairy cattle in 2019. The datasets on clinical mastitis in dairy cattle obtained by using the Disease and Treatment Diary web application is assessed. The conditions for editing these data are expressed. The files for the estimation of breeding values for the mentioned traits are described. The definition of the clinical mastitis as a trait for the breeding value estimation depends on the occurrence of clinical mastitis in the lactation of cow. The method used for the estimation is a linear animal model with the fixed effects of herd, year, calving period and parity and the random effects of the animal and the permanent environment of the cow. Single-step estimation method is employed to estimate genomic values. Results, estimates of genomic breeding values and their reliability, are presented. Genetic correlations between clinical mastitis and exterior traits in Holstein cattle close the report.