The ultra thin body (UTB) SOI architecture offers a promising option to extend MOSFET scaling. However, intrinsic parameter fluctuations still remain one of the major challenges for the ultimate scaling and integration of UTB-SOI MOSFETs. In this paper, using 3D statistical numerical simulations, we investigate the impact of random discrete dopants, body thickness variations and line edge roughness on the magnitude of intrinsic parameter fluctuations in UTB-SOI MOSFETs. The sources of intrinsic parameter fluctuations, which can be separated in simulation, will occur simultaneously within a single MOSFET. To understand the impact of these sources of fluctuation in an actual device, simulations with all sources of intrinsic parameter fluctuations acting in combination have also been performed.