Spectra of nearly 20000 point-like objects to a Galactic reddening corrected magnitude of i = 19.1 have been obtained to test the completeness of the Sloan Digital Sky Survey ( SDSS ) quasar survey . We focus on spatially unresolved quasars , which comprise 94 \% of all SDSS quasars to the main survey magnitude limit . The objects were selected from all regions of color space , sparsely sampled from within a 278 { deg } ^ { 2 } area ( effective area 233 { deg } ^ { 2 } ) of sky covered by this study . Only ten quasars were identified that were not targeted as candidates by the SDSS quasar survey ( including both color and radio source selection ) . The inferred density of unresolved quasars on the sky that are missed by the SDSS algorithm is 0.44 { deg } ^ { -2 } , compared to 8.28 { deg } ^ { -2 } for the selected quasar density , giving a completeness of 94.9 ^ { +2.6 } _ { -3.8 } \% to the limiting magnitude . Omitting radio selection reduces the color-only selection completeness by about 1 \% . Of the ten newly identified quasars , three have detected broad absorption line systems , six are significantly redder than other quasars at the same redshift , and four have redshifts between 2.7 and 3.0 ( the redshift range where the SDSS colors of quasars intersect the stellar locus ) . The fraction of quasars ( and other unresolved sources ) missed due to image defects and blends , independent of the selection algorithm , is \approx 4 \% , but this number varies by a few percent with magnitude . Quasars with extended images comprise about 6 \% of the SDSS sample , and the completeness of the selection algorithm for extended quasars is approximately 81 \% , based on the SDSS galaxy survey . The combined end-to-end completeness for the SDSS quasar survey is \approx 89 \% . The total corrected density of quasars on the sky to i = 19.1 is estimated to be 10.2 { deg } ^ { -2 } . The SDSS completeness restricted to z \gtrsim 3 quasars is expected to be considerably lower , and is a strong function of redshift . The determination of the global completeness is required for the statistical properties of quasars to i = 19.1 derived from the SDSS dataset , such as the luminosity function and correlation function , to be accurately determined .