-The aim of this study is to apply the main mathematical models used in activated sludge reactors, the Activated Sludge Model No. 1 (ASM1) and its variations (ASM2d and ASM3), to predict the behavior of a full-scale sequencing batch reactor (SBR) used for the treatment of domestic wastewater employing the software ASIM®. Two cycles were studied, the step-feed cycle and conventional filling. Samples were taken from the raw influent, from the reactor and from the treated wastewater, and these data were used to calibrate the models. The ASM1 model was the best model to represent the cycle with only an input, while model ASM3 was the best for simulating the scaled filling cycle. This work presents calibrated parameters for the two kinds of filling. The results of these simulations indicate that the calibration process succeeded and can be used as a model for future studies.