The objective of this work was to create mathematical models of the BioSID side impact test dummy, for use in side impact simulation studies. Two dummy models were created - a multibody model, and a finite element model. The models have been validated according to the procedures described in the BioSID User's Manual. The responses of both models were within the required corridors for most of the specified calibration tests, and during these test conditions the behaviour of the models correlated well with physical dummies.The models are now being tested in numerical side impact models of the vehicle. Each dummy model is particularly suited to different tasks: The multibody model is used in a lumped-mass model of the vehicle side structure, for studying the door padding and door intrusion characteristics. The finite element dummy model is implemented into finite element models of vehicles, allowing the vehicle-dummy interaction to be studied in much greater detail than is possible with physical testing or with lumped-mass models.Both types of modelling technique have inherent advantages and disadvantages. Examples from the models are used to highlight these traits, and recommendations are made regarding techniques which will improve the ability of mathematical models to represent vehicle occupants.