Einstein X-Ray Observations of M101

We present the Einstein X-ray observations of the face-on spiral galaxy M101. The global X-ray luminosity of M101 is L_x_ ~ 1.2 x 10^40^ ergs s^-1^ for D = 7.2 Mpc, consistent with the expected X-ray luminosity of normal spiral galaxies of its optical magnitude. The X-ray emission is mostly due to very luminous individual sources, with L_x_ > 10^38^ ergs s^-1^ each, most likely very massive accreting binary systems. The data suggest a deficiency of sources in the luminosity range of L_x_ 10^37-38^ ergs s^-1^, which would indicate that the luminosity distribution of the X-ray sources in M101 might be different from that of M31 or M33.