Mastitis is a significant disease in cattle breeding. Mastitis is divided into clinical and subclinical mastitis. Typical symptoms of clinical mastitis (KM) are swelling, redness, and soreness of the mammary gland, flakes in the milk, or milk-not-like secretion. The phenotypic relationships among Udder Depth as a conformation trait, the incidence of clinical mastitis, and somatic cells were analyzed in Czech Holstein cattle. The KM was considered an all-or-one trait with 0 (no KM case) and 1 (at least 1 KM case). The somatic cell count (SCC) was transformed into a somatic cell score (SCS) for normal data distribution. The phenotypic correlation of observed data for the characteristics ranged from -0.13 to 0.69. These correlations were referred to as phenotypic. There were proposed appropriate selection criteria for the selection of heifers. The optimal score of the conformation traits considering low incidence of KM mostly coincided with the optimal score of low SCS.