The invention provides Aryl substituted imidazoles, pyrazoles, pyridizines and related compounds of the Formula ##STR00001## where the variables are defined herein.Such compounds are ligands of C5a receptors. Preferred compounds of the invention act bind to C5a receptors with high affinity and exhibit neutral antagonist or inverse agonist activity at C5a receptos. This invention also relates to pharmaceutical compositions comprising such compounds. It further relates to the use of such compounds in treating a variety of inflammatory and immune system disorders.