Clinical and subclinical mastitis affects 30% of cows and is regarded as the most significant economic burden on the dairy farm reducing milk yield and quality and increasing culling rate. A proprietary Acoustic Pulse Therapy (APT) device was developed specifically for treating dairy cows. The APT device was designed to produce deep penetrating acoustic pulses that are distributed over a large treated area at a therapeutic level. This paper presents findings from a clinical assessment of this technology for the treatment of dairy cows with subclinical and clinical mastitis. In subclinical mastitis, a group of 116 cows from 3 herds were identified with subclinical intramammary infection and enrolled in the study; 78 cows were assigned to the treatment group and 38 cows to the control group. Significant differences (P<0.001) were found where 70.5% of the cows in the treatment group returned to normal milk production, compared with only 18.4% of the control group. Daily milk yields of the treated cows increased significantly (P<0.05) and the percentage of cows with log somatic cell count under 5.6 cells/mL was significantly higher (P<0.001). Milk of the infected quarters appeared normal with lactose greater than 4.8%, but this difference was not significant. Of the treated cows with identified bacteria, 52.6% of the quarters were cured, while in the control group only 25.0% (P<0.001). Specifically, all cows identified with Escherichia coli in the treatment group were cured, with 66.6% cured with no intervention in the control. Spontaneous cure of glands infected with coagulase negative staphylococci (CNS) and Streptococci was low while treatment successfully increased the cure of CNS from 13.3% to 53.8% and that of Streptococci from 18.2% to 36.4%. Of the 4 cows identified with Staphylococcus aureus, 3 were cured. The clinical mastitis study group included 29 infected cows that were submitted either to a gold standard antibiotic treatment subgroup of 16 cows (n = 16) or to an APT treatment subgroup of 13 cows (n = 13). A cure of 18.7% was shown for the antibiotic treatment, of which logSCC returned to <5.6 cell/mL and 56.2% were culled. A cure of 76.9% was shown for the APT treatment with only one cow culled (7.7%).