This invention generally relates to muscarinic receptor antagonists which are useful, among other uses, for the treatment of various diseases of the respiratory, urinary and gastrointestinal systems mediated through muscarinic receptors. Specifically, the invention relates to derivatives of azabicyclo compounds, including, for example, 6-substituted azabicyclo[3.1.0] hexanes, and 2,4,6-trisubstituted derivatives. The invention also relates to pharmaceutical compositions containing the compounds and the methods of treating the diseases mediated through muscarinic receptors.