An ultraviolet spectroirradiometer (UVS) has been used to measure downward-going solar flux in the 290- to 410-nm spectral region. Broadband pyranometers were used to measure the ratio of upward-going to downward-going flux in the 300-to 400-mn range to derive a band-averaged effective ground albedo. Use of these data with atmospheric scattering calculations, the ozone UV absorption cross sections, and the spectral O(1D) quantum yield allows the calculation of J0, the local photoproduction rate of O(1D) from O3. The photoproduction rate J0 varies strongly with effective ground albedo, total ozone, and solar zenith angle, and less with altitude. Results are consistent with photoproduction rate calculations taking ground albedo into account and show that accurate determination of J0 requires measurement of UV fluxes