Abstract: A pipeline pig comprises a central body member and a first drive member (26) mounted on the body member, the first drive member including a central annular support element (60) mounted on, to surround, the body member, and a plurality of circumferentially spaced primary drive elements (62) one end of each of which is secured to the support element (60) whereby the primary drive elements (62) extend substantially radially from the support element (60) and such that, in use, the other, free ends of the primary drive elements (62) engage the inner wall of the associated pipeline, each primary drive element (62) being capable of bending rearwardly of the direction of movement of the pig about the one end extent thereof to maintain engagement with the inner wall of pipelines within a range of diameters without increasing the drag thereon, the first drive member (26) further including a flexible backing disc (68) rearward of the primary drive elements (62) and adapted to seal against the inner wall of the pipeline