A variable geometry turbine comprising: a housing; a turbine wheel supported within said housing for rotation about a turbine axis; an annular inlet passage within said housing upstream of said turbine wheel and defined between respective radial inlet surfaces of first and second wall members; an outlet passage within said housing downstream of said turbine wheel; an array of vanes (329; 429) extending across the inlet passage, said vanes being connected to said first wall member (325; 425; 725); at least one of said first and second wall members being moveable along the turbine axis to vary the size of the inlet passage and/or at least one of said vanes being rotationally moveable about an axis that is substantially parallel to said turbine axis to vary the size of the inlet passage; at least one particulate filter (431a, 431b; 531; 631; 731a, 731b) being provided within said housing at a location such that said particulate filter can be contacted by particulate matter flowing through said turbine during use; said first wall member (325; 425; 725) defining a further radial surface (332; 732) opposite to said radial inlet surface (330; 430) and said at least one particulate filter being connected to said further radial surface (332; 732); said radial Inlet surface (330; 430) of said first wall member (325; 425; 725) defining one or more axially extending apertures which define an axial flow path for gas to flow through the first wall member (325; 425; 725) during use; characterised in that said at least one particulate filter (431a, 431b; 531; 631; 731a, 731b) defines one or more second openings (553; 655) arranged to axially overlie said one or more axially extending apertures such that said axial flow path extends through said second openings (553; 655). a housing; a turbine wheel supported within said housing for rotation about a turbine axis; an annular inlet passage within said housing upstream of said turbine wheel and defined between respective radial inlet surfaces of first and second wall members; an outlet passage within said housing downstream of said turbine wheel; an array of vanes (329; 429) extending across the inlet passage, said vanes being connected to said first wall member (325; 425; 725); at least one of said first and second wall members being moveable along the turbine axis to vary the size of the inlet passage and/or at least one of said vanes being rotationally moveable about an axis that is substantially parallel to said turbine axis to vary the size of the inlet passage; at least one particulate filter (431a, 431b; 531; 631; 731a, 731b) being provided within said housing at a location such that said particulate filter can be contacted by particulate matter flowing through said turbine during use; said first wall member (325; 425; 725) defining a further radial surface (332; 732) opposite to said radial inlet surface (330; 430) and said at least one particulate filter being connected to said further radial surface (332; 732); said radial Inlet surface (330; 430) of said first wall member (325; 425; 725) defining one or more axially extending apertures which define an axial flow path for gas to flow through the first wall member (325; 425; 725) during use; characterised in that said at least one particulate filter (431a, 431b; 531; 631; 731a, 731b) defines one or more second openings (553; 655) arranged to axially overlie said one or more axially extending apertures such that said axial flow path extends through said second openings (553; 655).