We report results of a serendipitous hard X-ray (3-20keV), nearly all-sky (|b|>10{deg}) survey based on RXTE/PCA observations performed during satellite reorientations in 1996-2002. The survey is 80% (90%) complete to a 4{sigma} limiting flux of ~1.8 (2.5)x10^-11^erg/s/cm^2^ in the 3-20keV band. The achieved sensitivity in the 3-8keV and 8-20keV subbands is similar to and an order of magnitude higher than that of the previously record HEAO-1 A1 and HEAO-1 A4 all-sky surveys, respectively. A combined 7x10^3^~sq.deg area of the sky is sampled to flux levels below 10^-11^erg/s/cm^2^ (3-20keV). In total 294 sources are detected and localized to better than ~1{deg}. 236 (80%) of these can be confidently associated with a known astrophysical object; another 22 likely result from the superposition of 2 or 3 closely located known sources. 35 detected sources remain unidentified, although for 12 of these we report a likely soft X-ray counterpart from the ROSAT all-sky survey bright source catalog. Of the reliably identified sources, 63 have local origin (Milky Way, LMC or SMC), 64 are clusters of galaxies and 100 are active galactic nuclei (AGN). The fact that the unidentified X-ray sources have hard spectra suggests that the majority of them are AGN, including highly obscured ones (N_H_>10^23^cm^-2^). For the first time we present a logN-logS diagram for extragalactic sources above 4x10^-12^erg/s/cm^2^ at 8-20keV.