This invention generally relates the derivatives of 3.6-disubstituted azabicyclo[3.1.0]hexanes of the following formula [IA]. The compounds of this invention can function as muscarinic receptor antagonists, and can be used for the treatment of various diseases of the respiratory, urinary and gastrointestinal systems mediated through muscarinic receptors. The invention also relates to a process for the preparation of the compounds of the present invention, pharmaceutical compositions containing the compounds of the present invention and the :h1ethods for treating the diseases mediated through muscarinic receptors.