The present invention provides compounds of general formula I: ##STR00001## or a pharmaceutically acceptable salt thereof, wherein R.sup.1, X, Z, R.sup.2, X.sub.1, Ar, n, R.sup.3 and R.sup.4 are defined generally and in subsets herein. Compounds of the invention are inhibitors of CCR8 and accordingly are useful for the treatment of a variety of inflammatory and allergic disorders.