Direct reprogramming of human fibroblasts to induced pluripotent stem cells (iPS) has been achieved by ectopic expression of defined transcription factors. Derivation of human fibroblasts however is a time consuming process and requires punch biopsies or isolation of patient foreskin. Here we use a polycistronic vector encoding Oct4, Klf4, Sox2 and c-Myc to generate iPS cells from from frozen peripheral blood of several donors. Genomic DNA analyses indicated that iPS cells were derived from mature T cells as well as myeloid donor cells. Inducing pluripotency in peripheral blood would allow utilization of easy to get samples from the adult and, more importantly, provide convenient access to numerous patient samples stored in blood banks. The latter is of major interest as frozen blood samples, when reprogrammed to iPS cells, would allow the retrospective molecular analyses of rare diseases.