Research in the field of gene-diet interactions as determinants of plasma lipid response to dietary interventions has accumulated a substantial body of evidence during the past decade. Several candidate genes have shown some promise as potential markers of individual dietary responsiveness. Among the best characterized are the APOE, APOA4, APOB, APOC3, and LPL loci. Other genes are being continuously incorporated to this most interesting search. However, in very few cases has consensus been achieved about the usefulness of genetic markers as clinically significant predictors of dietary response. The increased ability to generate genotypic information, in combination with the knowledge from the human genome project and more comprehensive experimental designs, will dramatically improve our capacity to answer many of our current questions. It will also help to prove that knowledge of an individual's genetic background will facilitate more precise dietary counseling and intervention, and more efficacious primary and secondary coronary heart disease prevention.