Zinc phenylphosphonate monohydrate takes up 1 mol of amine when contacted with liquid primary alkylamines. The mechanism of intercalation involves replacement of the coordinated water molecule by the amine molecules. Although the composition of the intercalate Zn(O3PC6H5)(RNH(2)) is consistent with the analytical and spectroscopic data, there exist discrepancies in the observed interlayer d spacings of the intercalate with respect to that in the host compound. The a spacing for the propylamine intercalate is in fact smaller than that in zinc phenylphosphonate itself. In order to understand this feature specifically and to explain the mechanism of amine intercalation in metal phosphonates in general, we have determined the structures of the intercalates. The structures of Zn(O3PC6H5)(RNH(2)), R = -C3H9 (1), -C4H11 (2), -C5H13 (3), were solved ab initio from X-ray powder diffraction data and refined by Rietveld methods. All the compounds are isostructural, and they crystallize in the monoclinic space group P2(1)/c with a = 13.9783(3) Angstrom, b = 8.791(2) Angstrom, c = 9.691(2) Angstrom, and beta = 102.08(1)degrees for 1, a = 14.698(4) Angstrom, b = 8.957(3) Angstrom, c = 9.712(3) Angstrom, and beta = 102.465(3)degrees for 2, and a = 16.267(3) Angstrom, b = 8.935(2) Angstrom, c = 9.695(2) Angstrom, and beta = 102.32(1)degrees for 3. The structures of these intercalates are new and are different from that of the host compound although all of them are layered. In the intercalate the zinc atoms are tetrahedrally coordinated as opposed to octahedral coordination in the host compound.