While the optical [1][2][3] properties of various ensembles of individual Si nanocrystallites (NCs) and the memory-charge storage (CS) characteristics of two-dimensional (2D) arrays of Si NCs [4] have been investigated by many researchers, relatively little attention was paid to the transport properties of 3D ensembles of such quantum dots (QDs) [5]. The interest in the last systems, however, is expected to follow the new basic physics that it reveals and the potential applications of such systems. Following the reasonable (though still controversial [6]) understanding of granular metals [7,8], where the electrical conduction takes place via metallic particles, additional significant insights into the transport mechanism [5,9] and new phenomena are expected in Si NCs due to the presence of confined levels [10]. In particular, the combination of Coulomb blockade (CB) effects and the quantum confinement (QC) restrictions can yield various resonant tunneling effects [11] as well as various quantum phase transformations [12] that are beyond the scope of this chapter. From the application point of view, one realizes that significant electroluminescence (EL) can come about only as a result of efficient transport in 3D ensembles of Si NCs [4,13,14] that are dense enough to yield strong light emission. Finding the conditions for the optimization of the luminescence and the transport is then the route to achieve efficient Si-based photoelectronic devices [15].In this chapter, we present a review on the electrical transport in the ensembles of Si NCs. Since we are concerned with the transport in 3D ensembles of quantum dots, we will only briefly review the main results obtained from lower dimensional ensembles (i.e., 1D-like [16, 17] or perpendicular to 2D arrays [18][19][20][21]) of Si QDs in order to provide a reference for the effects of the small size of the single Si NCs on the transport in ensembles of larger dimensions. We will see that in spite of many studies of these 0D-like and 2D systems, which are essentially associated with single isolated NCs, and their potential use as nonvolatile memories, only the basics of the Silicon Nanocrystals: Fundamentals, Synthesis and Applications. Edited by Lorenzo Pavesi and Rasit Turan