We describe the complexation of isolated and native lipoproteins by natural macrocyclic polymers of glucose ('cyclodextrins'). Treatment of serum with cyclodextrin produces an immediate flocculation of the lipoproteins. The formation of cyclodextrin-lipoprotein complexes was evident on agarose electrophoresis gels. The concentration-dependent ability of alpha-cyclodextrin to precipitate chylomicrons and very-low-, low-, and high-density lipoproteins was used for clarifying lipemic serum. Results for normal and lipemic patients' specimens for some routinely measured analytes showed a good correlation between cyclodextrin treatment and ultracentrifugation. Unlike the use of organic solvents or ultracentrifugation, the proposed system provides a simple, mild, non-hazardous, and effective means for removing interfering lipid particles from biological specimens.