This book covers various applications of aptamers as biosensors. The chapters are organized in three major groups: (1) general aspects of aptamers and their selection, (2) aptamers as biosensors, and (3) applications of aptamer biosensors. It is clear even from the Table of Contents that aptamers have been utilized in many types of analytical techniques, including electrochemical, atomic force microscopy, capillary electrophoresis, spectrophotometric, and fluorometric. These applications are well described. However, the chapters tend to be repetitive, often reviewing the same applications and published works several times with little or no discussion of other approaches, such as the applications of aptamer biosensors in microcantilevers, photoinduced electron transfer, aptamer-coated SAW sensors, and evanescent-coupled field-guide wave sensors.