Aim The effects of replacement of amino acid residue Va1156 with Gln or deletion in Gln235 on the capacity of apolipoprotein AI(APo AI) to promote cholesterol efflux from murine peritoneal macrophages.Methods Cultured mouse peritoneal macrophages were used. 3 H-oleate labled acetyl low density lipoprotein (ac-LDL) was employed as an inducer for foam cell formation. After macrophages were cul-tured with Apo AI, 3 H-cholesterol released from cells to the medium was measured by scintillation spectrom-etry.Results The replacement of Va1156→Glu did not influence the capacity of Apo AI to promote cellular cholesterol efflux. However, a deletion in the residue Gln235 significantly reduced the ability of Apo AI to promote cellular cholesterol efflux.Conclusions Amino acid residue Glu235 of ApoAI is important for cellular cholesterol efflux.