A positive correlation of the milk specific conductance (MSC) to the number of cells (r = 0.65) and to the content of chloride ions (r = 0.93) was found on the basis of an examination of 196 udder-quarter milk samples. As indicated by the closeness of the relationship to the number of cells, MSC measurement at a determination level of 41.8% has similar diagnostic effectiveness as the determination of the content of chloride ions (determination level 43.5%) and lactose content (determination level 42.8%), and much higher diagnostic effectiveness than the determination of titration acidity (determination level 23.4%). As indicated by the closeness of the relationship to the content of chloride ions, MSC measurement at a determination level of 86.7% has higher diagnostic effectiveness than the determination of lactose content (determination level 73.9%) and titration acidity (determination level 54.6%). In both comparisons, the highest diagnostic effectiveness was found in assessing the chlorine-sugar number (determination levels of 49.8% and 94.0%). The MSC value, corresponding to the cellulization of 500 . 10(3) cells per ml of milk, was determined from regression: 0.523 S . m-1. The diagnostic congruence of MSC with the number of cells in milk was 81.25%, and with the findings of mastitis test-NK only 54.0%. The variability of the measurements of MSC renders it impossible to use this measurement to indirect multi-step screening of milk cellulization. It is only realistic to distinguish two classes of the measured MSC values: negative and positive.