The primary sources of mastitis pathogens are infected quarters, chapped, sore, or eroded teat ends, and the environment. The major means of transfer of the most predominant mastitis pathogens is the milking routine. Methods are available to reduce the number of organisms normally transferred during each of the procedures. However, with the exception of teat cup pasteurization, the application of hygienic procedures in herds where teat dipping is practiced did not result in additional beneficial effects. Effectiveness of 4% chlorine, 0.5 and 1% iodine, and 0.5% chlorhexidine teat dips has been demonstrated in field trials and should be the preferred products in a mastitis control program. Most gram-negative organisms get on teats by direct contact with the bedding. In herds with clinical coliform mastitis, changing the bedding material has been associated with fewer clinical mastitis cases.