The identification of susceptibility genes offers unique insights into the pathophysiology of disease. Our understanding of the pathophysiology of preeclampsia suggests that a number of biological mechanisms are involved. Candidate gene studies have focused primarily on maternal genes, including those encoding proteins involved in blood pressure regulation and sodium homeostasis, factors affecting endothelial reactivity, coagulation factors, cytokines and their receptors. Genetic association studies comparing the frequency of genetic variants in cases and controls provide a more powerful strategy than linkage analysis for the identification of susceptibility loci in complex disorders. Fetal genotyping has been largely neglected in reported genetic studies of preeclampsia, although it is clear from epidemiological research that fetal genes have a part to play. The chief benefit of genetic studies in complex disorders is in providing clues to underlying molecular mechanisms. The potential rewards are commensurate with the effort involved.