Epithelial cells, which express FGFR2IIIb, bind and respond to FGF-1, FGF-7 and FGF-10, but not FGF-2. Stromal cells, which bind and respond to FGF-1 and FGF-2, but not FGF-7 and FGF-10, express PGFR2IIIc or FGFR1IIIc. Here we show that when both isolated FGFR2 beta IIIb and FGFR2 beta IIIc or their common Ig module II are allowed to affinity select heparin from a mixture, the resultant binary complexes bound FGF-1, FGF-2, and FGF-7 with nearly equal affinity. In addition, FGF-S and FGF-7 bound to both heparin-Ig module IIIb and IIIc complexes, but FGF-1 bound to neither Ig module III. The results show that in isolation both Ig modules II and III of FGFR2 can interact with heparin and that each exhibits a binding site for FGF. We suggest that the specificity of FGFR2IIIb and FGFR2IIIc is dependent on the cell membrane environment and heparin/heparan sulfate. Ig modules II and III cooperate both within monomers and across dimers with cellular heparan sulfates to confer cell type-dependent specificity of the FGFR complex for FGF.