In insects, developmental and reproductive rates are temperature-dependent and species-specific. Therefore, the effects of climatic changes can be different for host and parasitoid species, thus changing host-parasitoid population dynamics. Within the research co-operation KLIFF (www.kliff-niedersachsen.de) we investigated the impact of climate change on selected vegetable pests and their natural enemies in Lower Saxony, Germany. As model organism we selected two important agricultural pests, Brevicoryne brassicae and Aleyrodes proletella, and their respective parasitoids, Diaeretiella rapae and Encarsia tricolor. To model the impact of predicted climatic changes on pest-parasitoid interactions age-structured simulation models were developed in INSIM1 estimating changes in population size for each species during the course of a year. Based on temperature data simulated by the climate model REMO (MPI, Hamburg, Germany) the parameters were estimated for two future time periods, 2021-2050 and 2071-2100, and compared to parameters estimated for a reference time period (1971-2000). The relative changes in maximum population size and the occurrence of population peaks for each species were analysed for the Lower Saxony area to investigate regional differences. The simulations incorporate the interactions that occur naturally between the species and allow a comparison of the impact of climate change on pest-parasitoid interactions between the time periods.