The absolute quantum efficiency (QE) of two 1024 × 1024 pixel phosphor-coated (lumigen) chargecoupled devices has been measured in the band from 1216 to 5200 Å. It is found that the average QE is 17.7 ± 1.8% for the lot 1 detector and 18.1 ± 1.8% for the lot 2 detector in the band from 1600 to 3800 Å. The sensitivity rises on the long-wavelength side of the measurement band to 32% at 5200 Å and falls with the wavelength below 1600 Å. The two detectors have different spatial uniformity characteristics; both have a very uniform response (±2%) to 5200-Å flat-field illumination, although only one of the devices has a flat ultraviolet response. The read noise of these devices is 8 electrons (e(-)).