The electrical conductivity (EC) was measured in 42 samples of individual raw milk and 15 samples of Kareish cheese collected from outskirts of Assiut province. The average levels of EC in raw milk samples were 3.59±0.47 for cold months and 2.49±0.39 mS/cm at 25°C for warm months, respectively. There was a significant variation between EC in both cold and warm months. Also the contribution and correlations of the various components in cow's milk to its EC has been studied. The average level of EC in cheese samples were 5.89±0.24 mS/cm at 25°C. Approximately 19.10% of cold months milk samples, 9.52% of warm month's milk samples and 46.67% of Kareish cheese samples recorded an EC value ranged from 6.00-8.00 mS/cm. However, presence of NaCl in cheese whey sharply increases EC. The results suggested that clinical mastitis could be detected earlier by measuring changes in EC of milk. Also a considerable seasonal variation of EC in raw milk was demonstrated.