The three-amino acid insertion/deletion (I/D) polymorphism in the apoB signal peptide (27 amino acid versus 24 amino acid signal peptide) was evaluated as a possible risk factor for myocardial infarction (MI) in a case-control study population comprising 238 MI survivors and 547 controls. In controls, homozygotes for the deletion allele (DD) had the highest mean levels of both total cholesterol and low density lipoprotein (LDL) cholesterol (LDLC), the homozygotes for the insertion allele (II) had the lowest mean values, while the heterozygotes (ID) had intermediate mean levels (p