It was shown that equilibrium electrooptical properties (the Kerr effect) in solutions of disubstituted polyacetylenes poly(1-trimethylsilyl-1-propyne) and poly(1-trimethylgermyl-1-propyne) are related to the dipole structure of these polymers that is associated with the partial spiralization of their chains. A method of estimating the length of monomer unit sequences occurring in the same spatial configuration (stereoblocks) was developed. This method is based on the experimental measurement of the specific Kerr constant of disubstituted polyacetylenes. The sizes of stereoblocks in polymer chains that were synthesized with the use of various catalysts and that differ in the mean ratio of trans: cis C=C bonds, as estimated by the electrooptical method, were compared with the X-ray diffraction data on the same film polymers. There was good agreement between the results obtained by both methods.