Abstarct: Small-molecule organic semiconductors have an important position in organic electronics due to their applicability in devices such as organic light-emitting diodes, organic solar cells, and organic field-effect transistors. However, charge transport in these materials has a fundamental difference from crystalline semiconductors because of their amorphous structure, weak intermolecular interactions, and localization of charge carriers. In such an environment, charge carriers move through hopping between localized sites, and the energy of these sites appears as a distributed quantity due to structural and electrostatic inhomogeneity. The Gaussian disorder model is one of the basic frxameworks for describing this behavior; however, the assumption of site-energy independence makes this model limited in fully explaining the electric-field dependence of mobility, energy relaxation, and the occupied density of states. In this thesis, the correlated disorder model in small-molecule organic semiconductors is investigated. The main focus is that the energies of molecular sites in an amorphous film are not necessarily independent of one another, and electrostatic fields arising from molecular dipoles and multipoles can create a correlated and clustered energy landscape. Such a landscape affects the hopping pathway of carriers, energy relaxation, the shape of the occupied density of states, and the value of mobility. Within this frxamework, the difference between the available density of states and the occupied density of states has particular importance, because under real operating conditions of organic devices, carriers are usually extracted or recombined before reaching complete equilibrium. The examination of experimental evidence obtained from thermally stimulated luminescence and the results of kinetic Monte Carlo simulations shows that the narrowing of the occupied density of states in small-molecule organic materials is not well explained by the assumption of completely random disorder, whereas the model with spatial correlation provides a more consistent and realistic picture. In addition, the analysis of Miller–Abrahams and Marcus hopping rates shows that the outcome of transport modeling depends not only on the type of energetic disorder, but also on the choice of hopping rate, electronic coupling, reorganization energy, static and dynamic disorder, and energetic traps. Finally, multiscale modeling is introduced as a future pathway for developing the correlated disorder model; a pathway that can lixnk molecular structure, amorphous morphology, electronic properties, and device performance within a unified frxamework.