en Biological Sciences Biological Sciences Original Research: Clinical Science Original Research: Clinical Science Multiple sclerosis (MS) is a chronic inflammatory disorder of the central nervous system, with a complex etiology that includes a strong genetic component. The chromosome 19q 13 region surrounding the apolipoprotein E (APOE) gene has shown consistent evidence of involvement in MS. In a cross-sectional study, to show the APOE genotype and allele frequency in the MS population of Iran in comparison with the control group, we genotyped its polymorphisms (ε2, ε3 and ε4 alleles). The authors investigated 81 patients with clinically definite MS and 93 asymptomatic elderly volunteers. The frequency of the APOE allele in the MS population in comparison with controls was 9.3% vs. 0.5% for ε4,44.4% vs. 51.6% for ε3, and 46.3% vs. 47.8% for £2. The highest frequency of APOE genotype was from ε2/ ε3 with 66.7% vs. 94.6% and the lowest, £4/£4 genotype with 2.5% vs. 0%. The authors found significant differences in the distribution of ε 4 allele between patients with MS and controls (9.3% vs. 0.5% X2=15.2 df=2 p<0.001). The highest frequency of £4 allele in MS patients was in Pure Turkish (25.0% vs. 5.3 % ) ethnicity. There was no signifIcant relation between ethnicity and genotype. In the present study ε2/ε4, ε3/ε4 and ε4/ ε4 genotypes were more common in bout-onset cases compared to primary progressive cases, and the secondary progressive disease was higher in carriers of £4 allele. Also, the ε 2 allele was higher in relapsing remitting disease. Multiple sclerosis, apolipoprotein E, polymorphism, disease course, Iran. 0 0 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-298-69&slc_lang=en&sid=1 V HADAVI hvaleh2000@yahoo.com 20031947532846003481 20031947532846003481 Yes From the Department of Human Genetics & Anthropology, School of Public Health & Institute of Public Health Research, Tehran University of Medical Sciences, P.D.Box 14155-6446, Tehran DD FARHUD 20031947532846003482 20031947532846003482 No From the Department of Human Genetics & Anthropology, School of Public Health & Institute of Public Health Research, Tehran University of Medical Sciences, P.D.Box 14155-6446, Tehran MH SANATI 20031947532846003483 20031947532846003483 No the National Research Center for Genetic Engineering and Biotechnology, Tehran SM NABAVI 20031947532846003484 20031947532846003484 No the Shahed Medical University, M SEYEDIAN 20031947532846003485 20031947532846003485 No Tehran University of Medical Sciences, Roozbeh Hospital M HUSHMAND 20031947532846003486 20031947532846003486 No the National Research Center for Genetic Engineering and Biotechnology M YOUNESIAN 20031947532846003487 20031947532846003487 No Department of Environmental Health Engineering, School of Public Health & Institute of Public Health Research, Tehran University of Medical Sciences, Tehran, Iran.