The new Human Stemcca™ lentivirus reprogramming kit generates induced pluripotent stem (iPS) cells from human adult cells. The humanized version of the Stemcca lentivirus expresses human Oct4, Klf4, Sox2, and c-Myc factors from a single polycistronic transcript. It can be used to reprogram normal or diseased postnatal human skin fibroblasts. The kit helps reduce the number of viral integrations required for the derivation of iPS cells. This in turn helps to increase reprogramming efficiency and create more homogeneous, reproducible iPS cell populations. In addition, Stemcca Cre-excisable kits facilitate removal of the reprogramming vector, which has been shown to improve the developmental potential of iPS cells and significantly increase their capacity to undergo directed differentiation in vitro.