A wall-flow filter (10) for an exhaust system of a combustion engine comprises: a plurality of channels (4,6,8) in honeycomb arrangement, wherein at least some of the channels (6) are plugged (12) at an upstream end and at least some of the channels (4,8) not plugged at the upstream end are plugged (14) at a downstream end; an oxidation catalyst (16) on a substantially gas impermeable zone at an upstream end of the channels (4,8) plugged at the downstream end; and a gas permeable filter zone (22) downstream of the oxidation catalyst for trapping soot, characterised in that in an exhaust system, preferably a diesel exhaust system, the oxidation catalyst is capable of generating sufficient NO.sub.2 from NO to combust the trapped soot continuously at a temperature less than 400.degree. C.