The aim of this study was to investigate the effects of the use of Teranekron alone or in combination with intramammaryantibiotic therapy for the treatment of subclinical and clinical mastitis on the recovery rate from mastitis. The study material wascomposed of 177 mammary lobes of 63 Holstein cows with subclinical (groups S1 and S2) and clinical mastitis (groups C1, C2, C3,and C4). In all of the treatment groups, excluding group S2, the California mastitis test scores were determined to have decreased afertreatment (P < 0.05). In groups C1, C2, C3, and C4, which were treated for clinical mastitis, the somatic cell count (SCC) values wereobserved to have decreased. The decrease in SCC values was statistically signifcant except in group C2 (P < 0.01). While the SCC valueswere observed to have decreased in group S1 (P > 0.05), which was treated with Teranekron alone, the same values were found to haveincreased in group S2, which was maintained for control purposes (P < 0.05). This study demonstrated that Teranekron D6 could beused as an alternative therapeutic for the treatment of clinical and subclinical mastitis, as it is authorized for the use in cattle with awithdrawal period of zero hours for meat and milk.