The present invention provides a therapeutic agent for bladder irritative symptoms associated with benign prostatic hyperplasia comprising, as an active ingredient, a tricyclic compound represented by formula (I): ##STR00001## [wherein R.sup.1 represents a hydrogen atom, substituted or unsubstituted lower alkyl, substituted or unsubstituted lower alkoxy or halogen; X.sup.1-X.sup.2-X.sup.3 represents CR.sup.5.dbd.CR.sup.6--CR.sup.7.dbd.CR.sup.8, N(O).sub.m.dbd.CR.sup.6--CR.sup.7.dbd.CR.sup.8, CR.sup.5.dbd.CR.sup.6--N(O).sub.m.dbd.CR.sup.8, CR.sup.5.dbd.CR.sup.6--CR.sup.7.dbd.N(O).sub.m, CR.sup.5.dbd.CR.sup.6--O, CR.sup.5.dbd.CR.sup.6--S, O--CR.sup.7.dbd.CR.sup.8, S--CR.sup.7.dbd.CR.sup.8 or O--CR.sup.7.dbd.N; Y represents 13 CH.sub.2S--, --CH.sub.2SO--, --CH.sub.2SO.sub.2--, --CH.sub.2O--, --CH.dbd.CH--, --(CH.sub.2).sub.p--, --SCH.sub.2--, --SOCH.sub.2--, --SO.sub.2CH.sub.2-- or --OCH.sub.2--; and R.sup.2 represents a hydrogen atom, substituted or unsubstituted lower alkyl, substituted or unsubstituted lower alkenyl, substituted or unsubstituted lower alkoxy, amino, mono(substituted or unsubstituted lower alkyl)-substituted amino, di(substituted or unsubstituted lower alkyl)-substituted amino, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, substituted or unsubstituted aralkylamino, substituted or unsubstituted arylamino or a substituted or unsubstituted heteroalicyclic group] or a pharmaceutically acceptable salt thereof.