The past decade has seen remarkable progress in elucidating the clinical relevance of circulating tumor cells (CTCs). Evidence from numerous clinical studies has unequivocally demonstrated the importance of CTCs as harbingers of poor outcome. Despite these advances, the molecular nature of CTCs remains elusive. This is in part due to the difficulty in isolating pure CTCs away from blood cells. Recent advancements in rare-cell technology have provided solutions to the once daunting task of isolating extremely rare CTCs in the blood of cancer patients. This book presents different novel approaches for detection and purification of CTCs. In addition, the readers are introduced to new technologies for molecular profiling of CTCs, including techniques to overcome limitations posed by the paucity of cells and the biomolecules available for downstream molecular analysis. This book is particularly relevant to scientists and academicians who are interested in the field of CTC research. It provides an overview of the recent technological advances in CTC isolation and profiling. This work also includes discussions on pertinent issues regarding the biology of CTCs, and their potential utility as liquid biopsy for personalized medicine. We hope that this book stimulate further research and help advance our understanding of the molecular biology of CTCs.