During the previous few years, many high-speed LSI devices for signal processing have been introduced. This has made the problem of implementing digital filters, and wave digital filters (WDF) in particular, considerably easier. This paper briefly surveys the research carried out on LSI and non-LSI hardware implementations of WDF during the last few years. This paper also describes a modification to earlier work on LSI implementations that enables the realisation of WDF with poles of attenuation.