In recent years, many linear filters have been replaced by nonlinear filters, especially in case of impulse noise distorting. Stack filters, the class of non-linear filters are very interesting for easy hardware realisation and threshold decomposition property. The development of digital HDTV gives technological push in this area. Various of very efficient order-statistics filters such as median or LUM smoother are useful in many applications. In addition, these filters can be realised as stack filters. This paper gives a short review of the stack filter class.