Epitaxial garnet films containing many different mixtures of the rare earths have been prepared for materials and device characterization. In addition, several different types of circuits for propagating and manipulating bubble domains have been proposed and demonstrated. This paper reviews some of the recent progress in characterizing these circuits and materials with respect to mass memory applications. The approach under consideration utilizes a rotating magnetic field for bubble propagation and pulsed-current conductors for certain control functions, such as bubble generation, bubble annihilation, and bubble transfer from one propagation loop to another. The detection function is done with magnetoresistive elements. Operation at frequencies of at least 100 kHz is desired and has been obtained separately for each of the required functions, using particular combinations of circuits and materials. More detailed characterizations of the materials, the circuits, and their combinations are presently in progress in order to achieve all required functions simultaneously with a single material-circuit combination.