Objective. To investigate the effect of apolipoprotein B （apoB） and E （apoE） genetic variations on lipid profile at baseline （before treatment）

and also on the subsequent response to simvastatin therapy.Methods. Eighty-eight patients with hyperlipidemia were treated with simvastatin 5mg daily. The plasma levels of total cholesterol （TC） and low-density lipoprotein cholesterol （LDL-C）

triglyceride （TG） and apo B were measured pre-treatment and at the end of the 4th

8th and 12th post-treatment week. Polymorphisms of apoB at XbaI locus and apoE were determined by restriction fragment length polymorphism （RFLP）.Results. In all patients

relative frequencies of X- allele and X + allele were 0. 943 and 0. 057 for apoB gene respectively. For apoE gene the relative frequency of ε 2 allele was determined as 0. 182

ε3 as 0. 580 and ε4 as 0. 238. The reduction in TC level was more prominent in patients carrying X- allele than in those with X + allele following treatment （-23. 9% vs. -13. 6%

P < 0. 05）. Compared with patients carrying ε 3 or ε 4 allele

those with ε 2 allele showed a significantly higher percentage in reduction of apoB level after treatment （P < 0. 05）.Conclusion. The relative frequency of apoB X + allele is high in patients with hyperlipidemia

in whom the TC-lowering efficacy is decreased following treatment of simvastatin. The relative frequencies of ε 2 and ε 4 are also high in hyperlipidemic patients

and the e 2 allele is associated with reduction in apoB level during lipid-regulating therapy.