The differentiation of 3T3-L1 preadipocytes into adipocytes is one of the few well characterized model systems available to study cellular differentiation in culture. We cloned and determined the genetic organization of two murine stearoyl-CoA desaturase genes (SCD1 and SCD2), both of which are transcriptionally activated during preadipocyte differentiation, but are regulated differentially by diet in liver and other tissues, These genes are now being used as a model to study mechanisms of cellular differentiation, tissue-specific gene expression, and dietary regulation of gene expression, It is the objective of this article to provide a brief overview of some of the studies on the regulation of the SCD1 and SCD2 genes during 3T3-L1 preadipocyte differentiation, and also on their differential responses to dietary manipulations in liver tissue.