There is provided a salt of 1-cyclopropyl-8- methyl-7-[5-methyl-6-(methylamino)-3- pyridinyl]-4-oxo-1, 4-dihydro-3-quinolinecarboxylic acid selected from the group consisting of citrate, hemi-fumarate, maleate, L-tartrate, mesylate, hydrochloride, potassium, and sodium salts.