We present the design, fabrication and testing of a novel three dimensional (3D) Field Effect Transistor based on Single-Walled Carbon Nanotubes (SWNTs). Three Dimensional SWNT transistors are realized utilizing low temperature Dielectrophoretic (DEP) assembly. A 1mum thick conformal Parylene-C (poly-para-xylylene) layer is utilized as the gate dielectric with a non-local top gate electrode around the conducting channel. The preliminary results from 3D Carbon NanoTube Field Effect Transistors (CNTFET) display ambipolar behavior with more prominent p-type than n-type behavior. The transistor exhibits an on-to-off current ratio of ~3 x 104, a maximum transconductance of 0.061 mus, and a mobility of 85- 277 cm2/Vs. This 3D-CNTFET technology can be utilized to realize multi layer, compact and high density nanotube transistors for large scale nanoelectronic circuits.