The crystal structure of three incommensurately modulated gamma-brass related composite structures in the Pd-Zn-Pt system has been solved from X-ray single crystal diffraction data using a 3 + 1-dimensional super space description. The compounds PtxPd15-xZn54 (x approximate to 6, 7, 10) crystallize in orthorhombic superspace group Fmmm(alpha 00)0s0 (F = [(1/2, 1/2, 0, 0); (1/2, 0, 1/2, 0); (0, 1/2, 1/2, 0)] with the following fundamental cell dimensions: a = 4.265(1) angstrom, b = 9.132(1) angstrom, c = 12.928(2) angstrom, q approximate to 0.629a*; a = 4.284(1) angstrom, b = 9.151(2) angstrom, c = 12.948(4) angstrom, q approximate to 0.628a*; and a = 4.288(1) angstrom, b = 9.140(4) angstrom, c = 12.926(7) angstrom, q approximate to 0.627a*. Each structure is built by two sub-lattices-pentagonal antiprismatic columns parallel to [100] and a zigzag chain of Zn atoms running along the center of the column.