Chemokine receptor antagonists, in particular, 3,7-diazabicyclo[3.3.0]octane compounds according to formula (I) wherein R.sup.1-R.sup.3 and Ar are as defined herein are antagonists of chemokine CCR5 receptors which are useful for treating or preventing an human immunodeficiency virus (HIV) infection, or treating AIDS or ARC. The invention further provides methods for treating diseases that are alleviated with CCR5 antagonists. The invention includes pharmaceutical compositions and methods of using the compounds for the treatment of these diseases. The invention further includes processes for the preparation of compounds according to formula I. ##STR00001##