  We present the first results from an XMM-Newton serendipitous medium-deep
survey, which covers nearly three square degrees. We detect a total of 1022,
495 and 100 sources, down to minimum fluxes of about 5.9 x 10^-16, 2.8 x 10^-15
and 6.2 x 10^-15 erg cm^-2 s^-1, in the 0.5-2, 2-10 and 4.5-10 keV band,
respectively. In the soft band this is one of the largest samples available to
date and surely the largest in the 2-10 keV band at our limiting X-ray flux.
The measured Log(N)-Log(S) are found to be in good agreement with previous
determinations. In the 0.5-2 keV band we detect a break at fluxes around 5 x
10^-15 erg cm^-2 s^-1. In the harder bands, we fill in the gap at intermediate
fluxes between deeper Chandra and XMM-Newton observations and shallower
BeppoSAX and ASCA surveys.
