There are 271 milk samples collecting from 72 dairy cattle in Long Hoa dairy cattle raising cooperative, Can Tho city were tested by using CMT method. The testing result showed that 25.09 percent of cow udder lobes and 51.39 percent of cows were infected with latent mastitis. The factors such as: the methods of collecting milk, month of lactating and farrows affected significantly to the rate of latent mastitis. Other factors such as: herd size, cross-breed and milk yield were less influenced to the rate of latent mastitis.