EUROSID is the side impact dummy that has been designed and has now been almost completely developed by a group of European research laboratories working together under the auspices of the European Experimental Vehicles Committee (EEVC). It represents a bringing together of components and ideas from the three experimental sided impact dummies sponsored by the EEC₁ as part of their Biomechanics Programme. These were produced by APR (Peugeot-Renault), ONSER, and MIRA. This paper describes the evolution of the EUROSID dummy and discusses the advances in biofidelity, the responses of its various components to impact, and the types of measurements it can record.