Apparatus for delivering material into a patient includes a catheter having a proximal end and a distal end. Material, preferably of filamentary or thread form, is fed from a material supply into a Y-fitting having a main branch and a side branch. The side branch is connected to a source of driving fluid able to feed drive fluid under pressure into the material carrier so as to pull material forwardly and out of the distal end of the catheter. The assembly includes an inner cannula within which material is passed from the material source. This increases the speed of delivery of material though the device and reduces the amount of drive fluid which is required.