Анотация: Cows were monitored and sampled for clinical mastitis by the farmers themselves during a period of one and a half years. A total of 600 aseptic milk samples were collected when an incidence of clinical mastitis was observed and underwent bacteriological examinations. Records collected from the Israeli Herd Book during the mastitis episode included: Monthly milk and Somatic Cell Counts (SCC), the time of appearance of the mastitis as well as the rate of recurrence of clinical mastitis during the lactation period. The aim of this study was to quantify the direct damage derived from milk losses exclusively caused by clinical mastitis. The most severe effect of clinical mastitis was found when it occurred : (a) during the first 60 days of lactation (losses of 903 kg milk per lactation); (b) After parturition during the summer season (1350 kg milk per lactation); and (c) In case of 2 or more recurrences of clinical mastitis in the same cow, during the same lactation