Most bodies whose wave drags in supersonic flow have been calculated by linearised theory are such that the flows can be represented by a suitable distribution of sources. The present paper extends this idea by considering the drag problem for the general class of thin and slender bodies which can be replaced by sources only. The flow due to sources is necessarily acyclic, so there can be no local cross-stream forces on such bodies, since their presence would require the introduction of vortex elements.