The purpose of this research was to evaluate the use of an on-farm culture system in conjunction with the California Mastitis Test for the strategic treatment of subclinical mastitis in fresh cows and clinical mastitis. CMT showed high NPV indicating it was very effective in determining uninfected quarters. However, PPV were low resulting in many CMT+ quarters being uninfected; thus many uninfected quarters being treated also. Cure rates in both the fresh and clinical animals did not change when treatment was delayed for twenty-four hours while waiting for culture results This would indicate that waiting for culture results before instituting treatment does not affect treatment success. The on-farm culture system, in conjunction with the CMT, dramatically reduced the number of animals treated with antimicrobials as compared to basing treatment The purpose of this research is to evaluate the use of an onfarm culture system in conjunction with the California Mastitis Test for the strategic treatment of subclinical mastitis in fresh cows and clinical mastitis. A cost-benefit analysis will also be used to determine the economic feasibility of an on-farm culture system for commercial use.