The interfacial tension gamma between the coexisting isotropic and cholesteric phases of aqueous solutions of a rigid triple-helical polysaccharide, schizophyllan, was determined by the sessile drop method, as a function of the polymer molecular weight. The values of gamma are almost inversely proportional to the molecular weight of schizophyllan in accordance with theories for solutions of hard rods, but the experimental absolute values are much larger than the theoretical ones. This disagreement may be ascribed to the polydispersity in the molecular weight of schizophyllan samples used and also the attractive interaction among schizophyllan triple helices. Schizophyllan triple helices align parallel to the isotropic-cholesteric interface in the cholesteric phase near the interface, and this alignment direction agrees with the theoretical prediction for hard-rod systems.