Dr. Moshe Elitzur, at the University of Kentucky, will continue a program of theoretical studies of astronomical masers. The topics targeted for research include (1) protostellar disks and outflows in high-mass star formation; (2) the circumstellar shells of evolved stars; and (3) structure at the parsec and sub-parsec scales at the centers of starburst galaxies and active galactic nuclei. A major component of the proposed research is close collaboration with the observing teams conducting the relevant observations. Broader impact of the proposed research will result from the training of graduate students.