Point mutations in the receptor binding domain of low density lipoprotein may increase cholesterol levels in blood. Three mutations of Apo B-100 protein result in defective binding (Arg 3500 ----> [corrected] Gln, Arg 3500 ----> [corrected] Trp and Arg 3531 ----> [corrected] Cys). We estimated the frequency of Apo B point mutations (codon 3500) C9774T (Arg 3500 ----> [corrected] Trp) and G9775A (Arg 3500 ----> [corrected] Gln) in 179 atherosclerotic, 145 hyperlipidaemic individuals and 272 healthy individuals in the east Mediterranean region of Turkey. Lipid and lipoprotein levels were measured with routine biochemical analyser and Apo B mutation was detected using real-time PCR. Neither mutation was found. In this region, Apo B-100 protein mutations are rare and causes of hyperlipidaemia and atherosclerosis may therefore be unrelated to them.