We discuss the quantum statistical properties of exciton-polaritons in semiconductor microcavities. The nonlinear dynamics is treated within a model of interacting bosons for the signal, pump and idler modes. We focus on the regime of parametric amplification below threshold. We present the time evolution of the signal and idler modes towards their stationary solutions and evaluate the amount of squeezing of the radiation emitted out of the microcavity in a configuration, which is relevant for experiments. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)