Equations for explicit Hartree states of energy lower than that of conventional ground states for noninteracting Fermi gases are given for Fermi gases with attractive interactions. One-dimensional and three-dimensional cases are treated. Large static density waves are shown to exist in such Fermi gases, and the binding energy is derived therefrom. If the density waves are used with the variational theorem, their contribution to the binding energy is greater, and it is concluded that density waves are of great importance in nuclear matter. In the limit of weak attractive interactions, the Fermi surface will become a manyfaced polyhedron, each pair of opposite faces arising from a density wave. (D.L.C.)