Abstract: A method of cleaning a vehicle exhaust system filter (1), the filter (1) having a first end (11) and a second end (10) and comprising a plurality of elongate channels (6) containing debris (19) to be removed, comprises the steps of: (i) providing a chamber (14) having an outlet in fluid communication with the first end (11) of the filter (1); (ii) covering the second end (10) of the filter (1) to hinder fluid flow out of the second end of the filter; (iii) introducing a flow of liquid into the chamber (14); (iv) stopping the flow of liquid into the chamber (14) when the chamber and channels (6) of the filter are substantially filled with liquid; (v) introducing a pulse of compressed gas into the chamber (14), and (vi) uncovering the second end (11) of the filter (1) to allow the gas to force said debris (19) and liquid (17) out of the second end (10) of the filter (1). The invention also provides apparatus for use in the method.