Abrasive slurry jet micro-machining (ASJM) uses a premixed slurry of abrasive and water cut and mill a variety of ductile and brittle materials, usually at relatively low pressures and particle velocities. In this paper, a high-pressure (up to 250 MPa) slurry jet micro-machining (HASJM) system was used for the milling of micro-channels in Al6061-T6. It was found that this system provided a more uniform abrasive flow rate than an abrasive water jet micromachining (AWJM) system, which entrained air and abrasive to create the slurry. Consequently, micro-channels milled using HASJM displayed less variability in centerline roughness and waviness.