X-ray crystal structures are reported for two sterically crowded porphyrins: 3,5,7,13,15,17-hexaethyl-2,8,12,18-tetramethylporphyrin (6, H{sub 2}DAP) and (3,5,7,13,15,17-hexaethyl-2,8,12,18-tetramethylporphinato)nickel(II) (Ni6,NiDAP). In the NiDAP structure, steric crowding is relieved by the usual mechanism of the porphyrin adopting a nonplanar conformation. The crystal structure of H{sub 2}DAP is unusual, as it shows an essentially planar conformation of the porphyrin macrocycle. In this case, steric crowding of the meso and pyrrole ethyl groups is relieved by a novel elongation of the porphyrin macrocycle. In this case, steric crowding of the meso and pyrrole ethyl groups is relieved by a novel elongation of the macrocycle among the 5,15 axis. A detailed study is made of the solution conformations of H{sub 2}DAP, NiDAP, and the corresponding zinc(II) complex (ZnDAP), using optical spectroscopy, variable-temperature proton NMR spectroscopy, and molecular mechanics calculations. It is suggested that the two species observed in low-temperature proton NMR studies of H{sub 2}DAP and ZnDAP correspond to cis and trans conformations of the methyl groups of the meso ethyls, and not the syn and anti structures proposed previously.