Describes the gas and dust components of the interstellar medium in ionized regions, atomic clouds, and molecular clouds. Shows how data from optical, infrared, and radio wavelengths can be utilized to determine density, temperature, composition, and dynamics of the various phases of the ISM. Comparison of these results with theoretical models. Includes an overview of the processes that affect the evolution of the ISM including the incorporation of gas and dust into stars, the effect of HII regions and young stellar objects, and the return of matter from evolved stars and supernovae. Offered every even Fall semester.