The present invention provides a condensed furan compound of the formula (I): ##STR00001## wherein Ring X is benzene, pyridine, or the like; Y is an optionally substituted amino, an optionally substituted cycloalkyl, an optionally substituted aryl, an optionally substituted saturated heterocyclic group, an optionally substituted unsaturated heterocyclic group; A is a single bond, lower alkylene, lower alkenylidene, lower alkenylene or an oxygen atom; R.sup.3 is hydrogen or the like; and, R.sup.4 is hydrogen, or the like, or pharmaceutically acceptable salts thereof, which is useful as a medicament, particularly, as an activated blood coagulation factor X inhibitor.