The ability of electrochemical discharge machining (ECDM) to manufacture micro-features in materials that are difficult to machine, such composites, glass, and ceramics, has drawn a lot of interest. These materials are difficult to machine using traditional methods because of their great hardness, brittleness, or toughness. They are often employed in the aerospace, biomedical, MEMS, and microelectronics industries. By combining the concepts of electrical discharge machining (EDM) and electrochemical machining (ECM), ECDM is able to address shortcomings of conventional techniques. The assistance of ultrasonic vibrations to ECDM process enhances its performance by improving circulation of electrolyte and forming stable gas film. As a new machining technique, ultrasonic-assisted electrochemical discharge machining (UAECDM) appears to be used for machining non-conductive materials. This paper provides a brief description of the gas film formation in terms of bubble formation, its amalgamation and detachment, influential parameters of gas film stability followed by summary of investigations carried out using UAECDM.