The present study investigated genetic variation in the 3' flanking region of ApoA-I (PstI), the 3' untranslated region of ApoC-III (SstI) and intron 2 of ApoA-IV (XbaI) in 435 type 2 diabetes mellitus patients, divided according to the presence or absence of coronary heart disease (CHD). Uncommon allele frequencies (P2, S2, X2) were 17.5%, 32.5%, 16.2% and 29.5%, 17.9%, 13.8% in patients with and without CHD, respectively. Linkage disequilibrium (D' = 0.31-0.73, p<0.01) was observed in all diallelic pairs except XbaI/PstI and XbaI/SstI in patients having CHD. Haplotype analysis revealed that P1-S2-X1 is a susceptibility haplotype that increases the risk of CHD in diabetes (OR 2.85, CI 1.51-5.61), exacerbating risk (OR 3.57, CI 1.81-7.45) even after adjustment for confounders. The findings in the present study suggest that each unit of P1-S2-X1 in diabetes increases the risk of CHD by a factor of 1.37+/-0.307 (beta + SE), which is manifest in its multiplicative mode.