The ability of somatic cells to be induced to pluripotency by ectopic expression of defined transcription factors has altered the course of research in developmental biology and regenerative medicine. Somatic cell reprogramming has now been performed with numerous somatic sources with variable kinetics and efficiencies. In this chapter, we describe a protocol for generating induced pluripotent stem (iPS) cells from human fibroblasts or keratinocytes. We provide a step-by-step procedure detailing how to culture the initial somatic cells (i.e., fibroblasts or keratinocytes), produce retrovirus encoding each of the four reprogramming factors (i.e., Klf-4, Oct4, Sox2, c-Myc, or KOSM), and infect the somatic cells to produce iPS cells.