The basic concept of acoustical holography is to form (and if necessary record) a hologram using coherent sound waves and to reconstruct the hologram using coherent light. There are many variations on this concept including reconstructing the hologram with a computer and Bragg diffraction imaging. During the 5 years since the first publication on acoustical holography a wide variety of applications and methods have developed. After a brief statement of some of the theory influencing the general principles, this paper discusses some of the methods which have recently developed as useful methods in practical situations. Among the methods discussed are the liquid surface levitation method and Bragg imaging method applied to nondestructive testing and biomedical imaging; including array synthesis and scanning being applied to the underwater and seismic areas.