ZR is a refurbished (R) version of Z aiming to improve its overall performance, reliability, precision, pulse shape tailoring and reproducibility. Z, the largest pulsed power machine at Sandia, began in December 1985 as the Particle Beam Fusion Accelerator II (PBFA II). PBFA II was modified in 1996 to a z-pinch driver by incorporating a high-current (20 MA, 2.5 MV) configuration in the inner /spl sim/ 4.5 meter section. Following its remarkable success as a z-pinch driver, PBFA II was renamed Z in 1997. Currently Z fires 170 to 180 shots a year with a peak load current of the order of 18-20 MA. The maximum z-pinch output achieved to date is 1.6 MJ, 170 TW radiated energy and power from a single 4 cm diameter, 2 cm tall array, and 215 eV temperature from a dynamic hohlraum. ZR in turn will, operating in double shift, enable 400 shots per year, deliver a peak current of 26 MA into a standard 4 m /spl times/ 2 m Z-pinch load, and should provide a total radiated X-ray energy and power of 3 MJ and 350 TW, respectively, achieve a maximum hohlraum temperature of 260 eV, and include a pulse-shaping flexibility extending from 100 s to 300 s for equation of state and isentropic compression studies. To achieve this performance ZR will incorporate substantial modifications and upgrades to Marx generator, intermediate store capacitors, gas and water switches, water transmission lines and the laser triggering system. Test beds are already in place, and the new pulsed power components are undergoing extensive evaluation. The Z refurbishment (ZR) will be operational by 2006 and cost approximately $60M.