The authors evaluated the method of the determination of the electric conductivity of purchased milk for the estimation of the hygienic aspects of milk quality and for mass diagnosis of the inflammatory diseases of dairy cow mammary glands. The variability coefficient of duplicates varied from 1.37 to 3.09%. The study of the dependence of milk conductivity measurement on milk temperature revealed a statistically highly significant positive correlation between the values of these two factors. In the temperature range from 30 degrees C to 35 degrees C the coefficients of correlation ranged from 0.951 to 0.996. Furthermore, interference caused by milk acidity was examined during a five-day incubation of samples at 25 degrees C. A statistically significant difference was observed from the third hour of incubation (P less than 0.05) and a statistically highly significant difference from the fourth hour of incubation (P less than 0.01). The evaluation of the diagnostic value of the method of the measurement of electric conductivity in purchased milk revealed a positive correlation to the content of chloride ions (r = 0.69) and to the number of the cellular elements of milk (r = 0.33).