Crystal field excitations have been observed in the high temperature superconductors REBa₂Cu₃O₇(RE= Dy, Ho, Er, Tm) by inelastic thermal neutron scattering. For the Dy, Ho and Er compounds the crystal field parameters have been refined from initial estimates calculated with Newman's superposition model. These parameters have then been successfully used to calculate the specific heat capacity and polycrystalline susceptibility of the compounds. A series of neutron spectroscopy measurements have been carried out on the heavy fermion compounds CeX₂Si₂ and (CeLa)Ru₂Si₂ where X is a transition metal element. These experiments show systematic changes in conduction electron f electron interactions with both conduction electron number and lattice parameter. For the La substituted compounds the linewidth of the scattering shows a temperature dependence characteristic of the Kondo effect. Neutron spectroscopy of CePd₃ and four compounds CePd₃Bₓ(x < 0.32) shows scattering on two energy scales. For x < 0.25 the scattering consists of pair of quasielastic peaks with widths of order 10meV and im1meV. The broader linewidth decreases with boron content and is nearly temperature independent. For x= O the narrower line became inelastic at low temperatures in one sample. For x > 0,25 the scattering consists of a narrow quasielastic peak and a broad crystal field excitation from a Γ7 excited state with energy im3meV. The lowest spin-orbit transition in Sm³⁺ was measured in the metallic compound SmPd₃, the first observation of this excitation by inelastic neutron scattering. Spectra were also taken for the intermediate valence compound SmB₆ which shows no intermultiplet excitations. We conclude that these are obscured by fast valence fluctuations.