The general lipid-lowering action of the N-substituted phthalimide derivatives reported herein, as well as the activity of potassium phthalimide, implicates the phthalimide moiety as possessing hypolipidemic activity in rodents. Compounds containing substituents with chain lengths of four carbon or oxygen atoms showed the best hypolipidemic activity in the series tested. Tests involving 1-N-phthalimidobutan-3-one demonstrated a dose-dependent hypolipidemic action free of estrogenic side effects, with no apparent deposition of cholesterol in body organs, and with a high therapeutic index. Further work on the hypolipidemic activity of phthalimido, as well as other imido compounds, is underway.