This field study focused on the possible effects of increased milking frequency (milking four times a day in comparison with milking twice a day) on clinical and bacteriological cure rates of clinical, antibiotically treated mastitis cases. Parameters tested were clinical, microbiological and full (cytomicrobiological) cure as well as the development of milk yield after the clinical mastitis episode. Cows from a large dairy herd meeting the study criteria (n=93) were assigned to two treatment groups by a systematic randomization scheme (blocked by body temperature <=or >39.5 degrees C). Both groups were randomly divided by experimental treatments: a) antibiotic intramammary treatment and milking 2-times a day; b) antibiotic intramammary treatment and milking 4-times a day. Treatments were initiated before the culture results were known. Cows were surveyed and evaluated on days 1-6, 24 and 31. No significant differences between treatment and control groups regarding clinical cure, microbiological cure, full cure and milk production could be established. Applying a 4-times a day milking regime did not lead to any significant effect, either positive or negative. Therefore, the results suggest that milking 4-times a day as a supporting therapy for mild, moderate and severe antimicrobially treated mastitis cases cannot be recommended.