Low-density lipoprotein (LDL) particles were immobilized on the inner wall of a fused-silica capillary and used in a study of the interactions between LDL and neutral drugs in electrochromatography. The effect of coating parameters (pH, ionic strength of the coating solution, duration of the coating procedure) on the properties and stability of the coating was examined. The stability of the coating was highest when the pH of the coating solution was under the pI value of the LDL particles. Interactions of unmodified LDL coatings with drugs were compared with those of acetylated LDL coatings. Acetylation of LDL neutralizes the positive charge on the lysine residues of the protein component of LDL particles, and acetylated LDL was used as a reference to examine the effect of the positively charged amino acids in the unmodified coating. Under similar coating conditions, acetylated LDL coating yielded stronger EOF evidently due to the decreased number of positive charges on LDL particles. The interactions of the unmodified and acetylated LDL coatings with steroids aldosterone, testosterone, and progesterone were comparable, which indicates that the density of immobilized LDL particles is not appreciably altered by acetylation. As expected, the strength of the interactions between steroids and the LDL coating increased with hydrophobicity of the drug.