The most common technique used in silencing gene expression adopts a naturally occurring cellular process called RNA interference (RNAi), which uses a double-stranded RNA molecule to silence homologous endogenous genes by degrading their cognate mRNA transcripts. The presence of long double-stranded RNA molecules triggers this process, which ensues by first shortening the lengthy transcripts enzymatically followed by their incorporation into the RISC complex thus allowing it to find and degrade complementary mRNA sequences. In an in vitro setting, short interfering oligonucleotides are commercially synthesized and commonly transfected into mammalian cells through lipofection. This current chapter illustrates the silencing of PPARγ gene using RNAi in adherent mammalian cells.