Possible methods for the advance detection and warning of clear air turbulence by airborne devices are surveyed briefly. These include: active use of radar, microwaves, infrared and visible portions of the electromagnetic spectrum; passive use of infrared, millimeter waves and visible light; air temperature probes; electric field measurements; electric charging of aircraft; ozone detection; and microbaro-metric measurements. The state of the art of CAT detection and warning is still exploratory. No method has yet been demonstrated to give advance warning of CAT with a confidence level sufficient to justify operational use, and too little is known about the physical parameters of CAT to enable any one method of detection and warning to be singled out as the most promising. More basic research on the physics and meteorology of CAT itself is needed.