Abstract: A method of generating an abrasive liquid jet comprising a high pressure liquid jet and abrasive particles for performing working operations such as cutting and cleaning. The method involves the delivery of the abrasive particles to the high pressure liquid in a dense phase slurry. The dense phase slurry is in the form of a paste which can be delivered along a supply line. Typically, the dense phase slurry comprises a mixture of an abrasive material, water and a thickening agent. The liquid jet and the abrasive slurry are brought together in a nozzle assembly (10). The nozzle assembly (10) has a body (11) defining a chamber (17). The liquid is introduced under pressure into the chamber (17) as a liquid jet through a delivery nozzle (13). The dense phase abrasive slurry containing the abrasive particles is introduced into the chamber (17) through supply openings (23). An outlet (19) is provided from the chamber (17) through which of the liquid and abrasive slurry can issue as an abrasive liquid jet.