Fibroblast growth factor-18 (FGF-18) binds with FGF receptors-2 and -3. Compositions comprising an FGF-18 component can be used to target cells that express these receptors. Suitable targets include tumor cells that express constitutively activated forms of FGF receptors-2 and -3. For example, conjugates of FGF-18 and saporin can be used to target tumor cells that express FGF receptors-2 or -3, and to inhibit the proliferation of these cells.