We conducted preliminary crystallographic investigations and biologic studies on 5 synthetically grown preparations of monosodium urate monohydrate (MSUM) crystals including one preparation of urate spherulites. The 5 crystal preparations exhibited wide variations in morphology, size, surface area, and ultrastructure, but only a few changes in their biologic effects. When injected intraarticularly, urate spherulites were less phlogistic than most acicular forms. Since crystal-cell interactions and inflammatory responses are influenced by crystal size, morphology, and surface characteristics, standardization of methods of preparing MSUM crystals is, therefore, important, particularly when analyzing and comparing results from different research laboratories.