We present our experimental observations concerning lyotropic liquid crystal behavior and textures of the solutions of the two polystyrene-block-polyisoprene block copolymers in a truly neutral solvent (toluene). The block copolymers used either lamellar or cylindrical microdomains in bulk and also in solutions above the critical concentration (c(c)). The optical textures, such as fan-shaped texture, parabolic focal conic texture and oily streaks, which have been often observed in smectics or columnar phases of lyotropic law-molecular-weight liquid crystals, were observed in the solutions above c(c) enclosed in between two glass slides. This demonstrates that the smectic or columnar lyotropic phases are formed in the ordered solutions. Further, we discuss the origin of the formation of the lyotropic phases of the block copolymer solutions in relation to the microdomain structures of the solutions. (C) 2000 Elsevier Science Ltd. All rights reserved.