The following is a summary of the results obtained from the examination of milk samples submitted by practicing veterinarians for mastitis diagnosis during the period Nov. 1, 1946 to Nov. 1, 1947. The diagnoses were made largely on the basis of a cultural examination. In a few cases the history and the appearance of the secretion aided in the diagnosis where either E. coli or Aero. aerogenes was reported. The cultural methods consisted of plating the samples on ox blood agar, or in cases of contaminated samples, they were plated on both sodium azide-crystal violet blood agar and blood agar containing 7.5 percent sodium chloride.