Enumeration and molecular characterization of circulating tumor cells (CTCs) are valuable for cancer diagnosis, survival prognosis, and treatment guidance.However, current methods require extensive enrichment process before analyzing rare CTCs in human blood.We reported here a new approach for direct CTC detection in whole blood samples without cell sorting by using digital competitive allele-specific TaqMan PCR (dCastPCR) for rare mutations and RT-qPCR for cell typespecific genes.