This Note describes the most recent updates in RJARS (RAND's version of the Jamming Aircraft and Radar Simulation), previously reported in N-2727-1. RJARS is a many-on-many computer simulation in the C language involving aircraft, radars, jamming systems, offensive and defensive missiles, infrared and optical systems, and a command-control-communications system for the defense. Major modifications include improvements in the multipath and clutter models, radar waveforms other than ordinary pulsed radars, scanning patterns other than circular, and height finders. The program has been restructured to make it more efficient and more understandable to the user. This Note is an adjunct to rather than a replacement for N-2727-1.