The Einstein Extended Medium Sensitivity Survey (EMSS) consists of 835 serendipitous X-ray sources detected at or above 4 times the rms level in 1435 IPC fields with their centers located away from the galactic plane. Their limiting sensitivities range from ~5*10-14 to to ~ 3*10-12 erg.cm-2.s-1 in the 0.3-3.5keV band. A total area of 778 square degrees of the high galactic latitude sky (|b|>20) has been covered. The analysis has been performed using data from the Rev 1 processing system at the CfA. The resulting EMSS catalog is a flux-limited and homogeneous sample of astronomical objects that can be used for statistical studies. Here we present the table listing all the sources taken from the publication referenced below and the optical identifications. At present over 96% of the 835 X-ray sources have been successfully identified in the following proportions: active galactic nuclei (QSO's, quasars and Seyfert), 51.1%; BL Lacertae objects, 4.3%; clusters of galaxies, 12.2%; normal galaxies, 2.1%; cooling flow galaxies, 0.6%; Galactic stars 25.8%; and unidentified, 3.9%. Most of the individual optical counterparts are previously unknown objects and so constitute large statistical samples independent of previously selection methods. The contents of the table is described below. The sky coverage computed for a specific assumed source spectrum is also given under "Additional Information" below. For further details please see the published articles: Gioia et al. 1990, Stocke et al. 1991. Additional Information: The EMSS sky coverage. ---------------------- This sky coverage has been produced using the counts in the standard detection algorithm and assuming a power law spectrum with energy index = 1 and the measured Galactic hydrogen column density in the direction of each IPC pointing. We caution the user that this sky coverage is not appropriate for computation of functions like logN(>S)-logS, or Luminosity Functions of resolved sources, like clusters of galaxies or "normal" galaxies, nor of stars. The fluxes for these objects have been calculated either using extended counts, when appropriate, and/or different assumptions for the incident spectrum (see below). Limiting Sensitivity Area Covered (erg/cm**2/s) (sq. deg) 5.08E-14 0.09 6.09E-14 0.72 7.31E-14 2.54 8.78E-14 6.37 1.05E-13 15.1 1.26E-13 29.4 1.52E-13 55.2 1.82E-13 94.2 2.18E-13 139.4 2.62E-13 191.6 3.14E-13 249.5 3.77E-13 319.1 4.53E-13 402.0 5.43E-13 497.0 6.52E-13 582.9 7.83E-13 657.7 9.39E-13 711.8 1.13E-12 743.7 1.35E-12 762.7 1.62E-12 771.9 1.95E-12 775.7 2.34E-12 777.4 2.80E-12 777.9 3.36E-12 778.1 --------------------------------------------------------------------------------