Mastitis is one of the main diseases in dairy cattle that produces an inflammation of the mammary gland. It is causing a large economic impact due to the decrease in milk production and quality. The disease manifests itself in clinical, subclinical or chronic forms. A rapid diagnosis is essential, especially in cases of subclinical mastitis, as this form does not present any evidence of inflammation, which allows the disease to spread rapidly among other healthy animals and thus affects the production. An efficient method in order to determine which bacterial agent is involved in the infection is to culture milk samples collected from animals of the concerned properties. In 2005 the Animal Microbiological Diagnostic Center - CEDIMA of CAV / UDESC in Lages-SC started receiving milk samples from regions located towards the ridge and west of Santa Catarina. The present study aims to carry out a survey of samples received during the period of January 2005 to December 2015, and to determine the most prevalent micro-organisms in the samples. During this period, the laboratory received a total of 1309 samples, of which 183 showed no bacterial growth. Therefore, 1126 positive samples were recorded for bacterial agents, uncovering 22 different genus types. Staphylococccus sp. was the most prevalent one 47.15% (531/1126), with 24.06% (out of 271/1126) being identified as coagulase negative, and 9,59% (108/1126) as Staphylococcus aureus. The second most prevalent genus was Streptococcus sp. 17.85% (201/1126), with 6.83% (77/1126) Streptococcus sp., 4.08% (46/1126) Streptococcus equinnus, and 3.01% (34/1126) Streptococcus dysgalactiae. Other isolated genus types were also observed with lower prevalence: Corynebacterium sp. 7.28% (82/1126), Enterobacter sp. 5,95% (67/1126), Klebsiella sp. 4,17% (45/1126), Nocardia sp. 3,73% (42/1126), E. coli 3,46% (39/1126), Arcanobacterium sp. 2,66% (30/1126) and Prototheca sp. (microscopic algae), 1,5% (17/1126). The information obtained from this survey demonstrates that Gram positive bacteria are the most prevalent in mastitis representing a total of 79,48% (895/1126), whereas Gram negative bacteria represent a total of 19% (214/1126).