1. The blood and plasma conductance was measured in 157 blood samples. Of these, 101 were from hospital patients with a variety of clinical conditions, 33 were from normal individuals, and 23 were unclassified. 2. Blood counts were done on the same specimens. 3. An empiric equation, was found to give the red cell count from the conductivity measurements, wherein C1 = 10.49, and g is in millions per cu. mm. See PDF for Equation 4. A nomograph is presented to simplify the calculations of the red cell count.