Novel pharmaceutical composition for accelerating salivation and for prophylaxis and/or treatment of xerostornia, which comprises as an active ingredient a carbostyril compound of the formula (1), wherein R is a halogen atom, and the substitution position of the subsistuent on said carbostyril nucleus is the 3- or 4-position, and the bond between the 3- or 4-positions of the carbostyril nucleus is either a single bond or a double bond, or a pharmaceutically acceptable salt thereof. The pharmaceutical composition of the present invention exhibits an accelcrating activity of salivation, and is useful in the prophylaxis or treatment of Xerostomia or hyposalivation.