L-706,000, a class III antiarrhythmic compound, has been found to exist in several different crystalline structures including two anhydrous polymorphs, two dihydrated enantiotropic polymorphs, a monohydrate, and several organic solvent solvates. The isolation of the desired crystal modification, dihydrate type A, can be accomplished under thermodynamic or kinetic control depending on the conditions. Under kinetic control, the isolation depends on a suspended transformation of a metastable state, L-700,462, a thrombotic agent, has been found to exist in three crystalline structures: a monohydrate and two anhydrous monotropic polymorphs. Both anhydrous polymorphs, when hydrated, yielded the single monohydrate. Drying of the monohydrate, depending on the conditions and sample, will give either anhydrous form. The varying results obtained upon drying are, once again, indicative of the presence of metastable states and suspended transformations in connection with the solid state of L-700,462.