Different selection strategies were studied to improve milk traits and to reduce the frequency of clinical mastitis and somatic cell count. The results indicate that it is better to use both clinical mastitis and somatic cell count in the selection index to improve the resistance of animals to mastitis and to improve the quality of milk. Selection for protein yield simultaneously with selection against mastitis or somatic cell count would result in increased milk, fat and protein yields, increased protein content, decreased fat content and decreased frequency of clinical mastitis and somatic cell count. Maximizing the total net economic profit based on the current pricing system in Finland would not decrease somatic cell count or frequency of clinical mastitis.