This study utilized daily records of 2000 Egyptian Holstein dairy cows. The productive, reproductive and economic data during a whole lactation season were recorded for healthy and mastitis cows. Two risk factors for mastitis were included, parity and season of calving. Mastitis cows had significant (P<0.05) decreased average daily milk yield (26.25 kg) and 305 day milk yield (8006 kg) compared to healthy cows (28.95 and 8829 kg, respectively). Mastitis cows recorded higher calving interval compared to healthy one (413.7 vs. 352.2 days). There were significant (P<0.05) increases in total variable costs and total costs of mastitis cows compared to healthy cows. Significant differences (P<0.05) were recorded for partial and collective efficiency measures, veterinary supervision as percent from costs, where high estimates were calculated for mastitis cows (0.89 and 0.80, respectively). Also the total veterinary management as percent from total costs showed more increase in mastitis cows compared to healthy contemporaries (4.22 vs. 2.68%). The mastitis cows recorded decreased total returns / total cost % versus healthy cows (108.7 vs. 121.4%). Finally, it could be concluded that mastitis had detrimental effects on the productive and economic efficiency of the dairy farms. پرونده مقاله