Disclosed are imidazonaphthyridine derivatives represented by formula (I)

wherein:
   R¹ represents lower alkyl or substituted or unsubstituted aryl; and
   X-Y-Z represents

wherein R² represents hydrogen, lower alkyl, alkenyl, aralkenyl, or -C(R⁵)H-(CH₂) n -R⁴ (wherein R⁴ represents substituted or unsubstituted aryl, substituted or unsubstituted pyridyl, substituted or unsubstituted furyl, hydroxy-substituted lower alkyl, lower alkanoyloxy, morpholino, lower alkanoyl, carboxy, lower alkoxycarbonyl, cycloalkyl, hydroxy, lower alkoxy, halogen or NR⁶R⁷ wherein R⁶ and R⁷ independently represents hydrogen or lower alkyl; R⁵ represents hydrogen, lower alkyl, or phenyl; and n represents an integer of 0 to 3); and R³ represents hydrogen, mercapto, hydroxy, lower alkyl, or aryl
and pharmaceutically acceptable salts thereof.
The compounds show a potent anti-inflammatory, anti-allergic and broncho-dilative activity.