Mastitis due to mycoplasma has been reported sporadically from several countries in Europe, Australia, Israel, New Zealand, and many states in the United States. Most reported occurrences are due to Mycoplasma bovis, but 5 other mycoplasmas are reported to cause mastitis. A total of 5 species of mycoplasma have been isolated from cows with mastitis in California. Therapy trials with M bovis infections have not been encouraging. Recovery is slow, and shedding of mycoplasma into milk of apparently recovered cows for an indefinite period is common.