This renewal proposal for the study of, "High Intensity Laser-Atom Interactions", calls for a joint theoretical and experimental study of atoms irradiated by intense optical fields. The experiments will focus on high harmonic generation (HHG) and on ionization in intense, short optical pulses. The measurements of harmonic coherence will be extended and high-order harmonics will be used to begin a new series of continuum saturation experiments. Recent findings on harmonic angular distributions will be extended by re-imaging the harmonics which emerge from the focus, measuring their spatial coherence using a Young's two-slit interferometer, and making a high resolution study of the angular spectral distribution. Theoretical work will continue to extract new information about strong-field atomic behavior during MPI and high-harmonic generation.