Abstract The crystal structure of zinc citrate [Zn(II) (C 6H 5O 7) 2·4NH 4 +] shows isolated zinc ions octahedrally coordinated to two equivalent citrates via a central hydroxyl, central carboxyl, and one terminal carboxyl from each citrate. The clusters are linked through hydrogen bonds to ammonium ions in the lattice. The structure is distinctly different from that of other divalent cation triply ionized citrate complexes, which are polymeric. Crystal data : space group P2 1/ C, a = 8.784(3) Å, b = 13.499(4) Å, c = 9.083(3) Å, β = 113.4°(1), V = 988(1) Å 3. Citrate has been identified as the low molecular weight ligand that complexes zinc in human milk; this may be of interest in relation to intestinal zinc absorption.