Abstract: An abrasivejet nozzle assembly is disclosed which is particularly suitable for drilling small diameter holes in a workpiece. Such assemblies include a mixing region wherein abrasive particles are entrained into a high velocity waterjet formed as high pressure water is forced through a jet-forming orifice. Among the unique features of the nozzle assembly are an inwardly tapered abrasive path just upstream of the mixing region, flushing conduits immediately upstream and downstream of the mixing region, and a venting passageway upstream of the mixing region which prevents the backflow of abrasive dust towards the jet-forming orifice.