This book presents the design of digital logic circuits using carbon nanotube field effect transistors (CNTFET). CNTFET is a promising device in the nanometer regime which utilizes a semiconducting carbon nanotube (CNT) channel between the source and drain terminals. Due to the excellent electrical properties of CNT it can offer very high speed integrated circuits. Starting with the basics of CNT and CNTFET this book discusses the modeling of CNTFET using Verilog-AMS language. The design of the basic logic gates is presented. The designs are simulated to verify their functionality and extract the speed and power performances. The design of reconfigurable logic circuits using transmission gate based logic is also presented. A ring oscillator circuit has been designed using CNTFET and it is found that the circuit can operate at very high frequency of 114 GHz.