Guide lines are presented for the selection of promising new acoustooptic materials for device applications. Previously, the selection of materials was based primarily on availability and intuition. Now it is possible to estimate an approximate acousto-optic figure of merit for a material knowing only its chemical composition and density. One of the first applications of these guide lines led to a detailed evaluation of lead molybdate, PbMoO4, a material known to have certain desirable physical properties. The results verified that PbMoO4has a high figure of merit, considerably greater than LiNbO3though somewhat less than α-HIO3. In addition to a high figure of merit, a material must also have a low acoustic loss if it is to be useful for device applications. The relationship between the acoustooptic figure of merit and acoustic loss is explored. Although only limited loss data are presently available, it is concluded that a high figure of merit and low loss are compatible material properties for applications below approximately 0.5 GHz. However, as future applications call for higher frequency operation, it appears that a tradeoff between low acoustic loss and high figure of merit will be required.