Aim of this book is to summarize the concepts and applications of CNT based DNA biosensors. Biosensors are quick analytical devices and play important roles in daily life especially in biomedical field. DNA biosensors and gene chips are of major interest due to their tremendous promise in biomarker based diagnosis of diseases. Application of nanomaterials has further enhanced the efficiency of these devices.This pocket size, compact book will be helpful for those involved in the research, teaching, learning, and practice of biosensing, based on various nanomaterials in biomedical and clinical applications. It emphasizes on unique properties of CNTs being used in fabrication of DNA biosensors for ultrasensitive biosensing in clinical diagnosis.