The etiology of SLE appears to be exceedingly complex and possibly heterogeneous, with genetics and environment both making substantial contributions. A schematic representation of potential mechanisms is depicted in Figure 2. We may not fully understand the pathogenesis of this disease until we unravel the relative contributions of each component to the development of SLE. While genetic mechanisms involved in SLE remain obscure, we now have available elegant laboratory techniques for analysis of genetic loci as well as computer technology which permits simulation and analysis of the transmission of complex genetic traits among multiple families and demographic groups. What remains is the painstaking task of collecting families multiplex for SLE and analyzing multiple sets of clinical, serologic, and genetic data within and between these pedigrees. Such studies are currently underway and will hopefully increase understanding of this enigmatic and complex autoimmune disorder.