The present invention relates to acylamino-substituted heteroaromatic compounds of formula I, ##STR00001## wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4 and R.sup.5 and X are as defined herein, to pharmaceutical compositions comprising such compounds, to methods for the stimulation of the expression of endothelial NO synthase, and methods of treatment comprising administering such compounds.