A series of 5,5-diaryl-2-thiohydantoins and 5,5-diaryl-N3-substituted-2-thiohydantoins related to 5,5-diphenyl-2-thiohydantoin (DPTH) were investigated as potential hypolipidemic agents with the goal of increased potency over DPTH itself. In the 5,5-diaryl class, the best results were obtained by substituting two pyridyl rings for the phenyl rings found in DPTH. The resulting compound, 5,5-bis(2-pyridyl)-2-thiohydantoin, DPYTH (5), had slightly better activity than DPTH in lowering liver cholesterol values. Further modifications to DPYTH (5) are underway and will be the subject of a future report. In the N3 nitrogen-substituted series one compound, 5,5-diphenyl-N3-n-butyl-2-thiohydantoin, DPBTH (7), showed promise during initial screening, but when analyzed in a dose-response study, its activity was considerably less than that of the parent compound DPTH.