From the Publisher's Website:
What if ghosts aren't really supernatural concepts, but creatures with their own biology? And if ghosts have their own biology, then using scientific principals, they can be thwarted - if not destroyed, at least captured. And if ghosts can be captured... well, then somebody can get rich doing it. Enter the Ghostbusters. Hobbled together by a group of misfit scientists, they attempted to use parapsychology for profit and, at least some of the time, succeeded.
In the 80s, Ghostbusting was a novelty. The end of the world brought on a lot of supernatural phenomena and, thanks to a lot of strange science and the Ghostbusters, was narrowly averted. By the end of the 80s, Ghostbusters were dealing less with the supernatural and more with problems like New York "not giving off a good vibe." The Ghostbusters were called upon again to do something about it and they moved pieces of NY's monuments to do it.
Life as a Ghostbuster is never predictable. The wax and wane of supernatural activity seems to vary without rhyme or reason - the 80s was rife with supernatural phenomena but there were entire years that were actually quite boring. At least, for a Ghostbuster.
As the world changed, so too did the nature of Ghostbusting. With a heightened awareness for global terrorism, the psychic energy matrix of the Earth is boiling with anger, fear, and hate - ghosts are more common than ever before. And what do you need when the world is gripped in fear and suspicious of everything that moves? You need a Ghostbuster: a man or woman who, backed by nuclear weapons, blasts a stream of barely harnessed energy at whatever you're afraid of, and do it with a smile and a small service fee.
Ghostbusters: Who Ya Gonna Call? is a d20 Modern RPG supplement that contains: 5 new allegiances, 7 new occupations, one advanced class (the elite Ghostbuster), new uses for old skills, 2 new feats, a bevy of new weapons and equipment (including proton packs and ghost traps), action point rules, planar travel, and monster classification.