Laminated plastic microfluidic components are being developed for; biological testing systems. and chemical sensors. Applications include a DNA thermal cycler, DNA analytical systems, electrophoretic flow systems, dialysis systems, and metal sensors for ground water.. This article describes fabrication processes developed for these plastic microfluidic components, and the fabrication of a chromium metal sensor and a microdialysis device. Most of the components have a stacked architecture; Using this architecture, the fluid flows, or is pumped through; as many as nine laminated functional levels: Functions include pumping, mixing, reaction, detection, reservoirs, separations, and electronics. Polyimide, poly(methylmethacrylate) (PMMA), and polycarbonate materials with thickness between 25 and 125 mu m are used to construct the components.This makes the components low cost, inert to many biological fluids and chemicals; and disposable. The components are fabricated by excimer laser micromachining the microchannel patterns and microstructures in the various laminates. In some,cases, micropumps are integrated into these components to move the fluids. Vias and interconnects are also cut by the laser and integrated. with micropumps. The laminates are sealed and bonded by adhesive and thermal processes and are leak tight. The parts withstand pressures as high as 790 kPa. Typical channel widths are 50 to 100 mu m; :with aspect ratios near 5.