An evaluation of entropies and enthalpies of transition and fusion and a comparison of X-ray diffraction patterns and IR spectra of polymorphic forms of structurally related compounds were undertaken to obtain information which might prove useful in correlating the frequency of occurrence of polymorphism with certain aspects of chemical structure. Sixteen sulfonamides were selected for study. The screening procedures used in this research identified polymorphism in eight compounds and solvates in two compounds. The p-amino group, the acidic N1-hydrogen atom, and the oxygens of the sulfonamide group have been implicated in the various hydrogen-bonding arrangements which distinguish one polymorphic form from another. It is postulated that electron-withdrawing and electron-donating groups at the N1-position influence the strength of the hydrogen bonds which form and, hence, the tendency of these compounds to exhibit more than one crystalline form. In some cases, however, minor alterations in structure result in disproportionate changes in the compactness of the crystal lattice, and this fact makes it difficult to develop broad generalizations applicable to large groups of compounds.