Granularity of the Sky at 15-25 KeV

Deep exposures at energies greater than 15 keV have been obtained incidentally as paired background fields for the HEXTE clusters of the Rossi X-Ray Timing Explorer. By measuring differences of a large number of these fields, which are separated by 3 or 6 degrees, we have begun to detect the fluctuation level of the diffuse x-ray background on the 15-25 keV band. From the approximately eight million seconds of data analyzed to date we have obtained a measurement of the fluctuation RMS at two sigma significance. This is consistent with an extrapolation from the HEAO-1 measurements on the 2-10 keV band.