[en] In the literature, one finds several models for control of redox properties in groundwater. The proposals for redox controlling substances include iron oxides, chlorites, methane, pyrite and polysulphides. The CRACKER program, which has been successful in modelling of observed Aespoe groundwaters has been used to investigate the influence of several redox control models on the modelled properties of present and possible future Aespoe groundwaters. In the simulations, one or more of the possible redox reactions have been prevented from occurring. The groundwater has then been assumed to react with minerals distributed in the fracture walls. Due to the discreteness of mineral grains, a certain amount of fluctuations in groundwater properties is occurring. The process of sampling water for measurement has been simulated by letting about 900 waters from different locations mix. It has been found that some of the models have difficulties in explaining important groundwater properties, while other models perform quite well. With identical mineral sets, the properties of future groundwaters have been simulated. It is found that some changes in groundwater properties at elevated temperatures may be of importance for assessment of the safety of a future repository for spent nuclear fuel. The difference in behaviour is caused mostly by the fact that the solubility increases with temperature for some minerals, while it decreases for other minerals. (author)