Global conformations of chiral polyisocyanates were discussed in terms of light scattering and viscosity data collected for stereospecifically deuterated poly(hexyl isocyanate)s, poly((R)-2,6-dimethylheptyl isocyanate) (PNIC), and copolymers of hexyl isocyanate (HIC) with (R)-2,6-dimethylheptyl isocyanate (NIC). The light scattering data and viscosity data obtained were analyzed consistently in the framework of the worm-like chain model. The persistence length q was the same for PHIC and deuterated PHIC, but increased with the mole fraction of MC in the HIC-NIC copolymers, e.g. from 41 to 56 nm in hexane at 25 degrees C. The results were not detailed enough to substantiate the broken worm model in line with the helix reversal model of Lifson et al. Gel permeation chromatographic behavior of the polyisocyanates was also examined, so that it could be used for the determination of the molecular weight distribution of a sample with a very minute amount (at most 1 mg or less).