Theoretical calculations of K'o are available in the standard literature for a very large number of chalcogenides. At least, until a few years ago, experimental data were available only for four of these compounds. For these four cases, the experimental value is about 40% higher than the corresponding theoretical values. In the light of this large discrepancy, we carry out the calculations, using the Born-Mayer theory. Our values are considerably higher than the old theoretical values referred to above, except for BaO. The discrepancy between our theoretical values and the experimental values in the three cases, for which the data are available is considerably smaller than for the earlier calculation. The discrepancy for BaO is now a little more. Apart from this, in one or two other cases, there is considerable difference between our calculation and the earlier ones. Experimental measurements for these cases and a few more would help in clearing up the situation.