The advanced state of development of molecular design and synthetic chemistry of porphyrins and related molecules makes these compounds good candidates for technological appli cations, in which well characterized and designed structures and properties are required. In particular, 2-dimensional molecular level control of porphyrin array structures should reveal new aspects of nanotechnology. In this review, recent research on porphyrin assemblies, including 2-dimensional porphyrin arrays, is described with emphasis on phenol- and quinone-substituted tetrapyrrole units. A series of research aimed at developing strategies for preparation of porphyrin molecular arrays, where several novel aspects of molecular arrays, including phase transitions, ordered 2-D phase boundaries, and hydrogen-bonding networks, are introduced.