ABSTRACTCertain aspects of the physical chemistry of solutions rodlike polymers are reviewed. The range of concentrations includes infinite dilution ([ŋ]c<<l), dilute solutions ([ŋ,]c<l), moderately concentrated solutions (l<[ŋ]c<[ŋ]cNI), and concentrated solutions (c<cN,), where [ŋ] is the intrinsic viscosity and cNI. is the concentration required for a stable nematic phase. Studies of chain conformation are emphasized at infinite dilution, and rheological behavior is emphasized for more concentrated isotropic and nematic solutions. Both theoretical and experimental considerations are included.