Apolipoprotein A5 gene (APOA5) variants are associated with increased plasma triglycerides, a risk factor for the metabolic syndrome (MS). but a correlation with apolipoprotein C3 (APOC3) genotypes is controversial. We investigated the correlation of APOA5 genotypes with plasma apoA5 levels and APOC3 genotypes in MS patients from a Romanian Population APOA5 (-1131T>C, c56C>G) and APOC3 (-482C>T, -455T>C) genotypes and plasma apoA5 concentration were determined in MS patients and healthy subjects. Results showed higher apoA5 levels ill plasma and high density lipoproteins (HDL) from MS patients, carriers of the APOA5 c56G allele, as compared to MS carriers of APOA5 -1131C allele or the common genotype. ApoA5 levels in plasma and HDL-fraction from MS carriers of -1131C and c56G alleles correlated positively with plasma triglycerides levels and negatively with HDL-cholesterol in MS carriers of c.56G allele Higher frequencies of APOC3 -482T and -455C alleles were detected in MS patients compared with healthy subjects We demonstrated the association of APOC3 -482T and -455C with APOA5 -1131C allele, but not with c.56G allele in MS patients We propose APOA5 c56C>G as a functional polymorphism, whereas APOA5 - 1131T>C is not all independent risk factor, being effective only when associated with APOC3 -482T or -455C alleles. (C) 2009 Elsevier Inc. All rights reserved