The present invention provides compounds, compositions and methods for the selective inhibition of cathepsin S. In a preferred aspect, cathepsin S is selectively inhibited in the presence of at least one other cathepsin isozyme. The present invention also provides methods for treating a disease state in a subject by selectively inhibiting cathepsin S. More particularly, the present invention provides compounds having Formula I: ##STR00001## wherein Q is morpholinyl; and A, R.sup.5, R.sup.6, R.sup.7, R.sup.8, R.sup.9 and Ar are substituents.