Theoretical and experimental investigations of the linear and nonlinear space-charge field effects in photorefractive materials are reviewed. In particular, the aim is to explore the dynamics of space-charge field formation under the influence of various enhancement mechanisms such as dc and ac electric fields, and the running holographic grating technique. Both the linear aspects and the nonlinear parametric processes are investigated. The analysis is based on the phenomenological band transport model in the single-carrier and one-step excitation version. Although many different physical effects are treated on the basis of these dynamical equations, it is demonstrated that the underlying perturbational approach appears as the governing principle both in the analytical derivations and in the physical interpretations. The principles of the recently formulated space-charge wave theory are outlined and applied to explain various nonlinear phenomena such as photorefractive parametric oscillation and amplification, and the effect of quadratic recombination.