In order to give a more scientific basis to the health risk assessment of residues of environmental contaminants, agrochemicals and natural toxins in food products, it is important to increase our knowledge of the mechanisms behind the toxic effects of both single and, especially, mixtures of compounds, as well as of actual exposure levels. In addition, it is important to improve the techniques that are currently used to extrapolate animal data to humans by performing proper species comparisons. In vitro models offer new opportunities for us to fill in some of these gaps in our knowledge. Furthermore, in view of the ever-increasing number of chemicals that need to be monitored, in vitro models can be used as bioassays, thereby detecting compounds or groups of compounds by their biological activity rather than by their physicochemical properties. In this review article, we describe some of the recent advances in this field, including the development of bioassays for environmental contaminants with oestrogenic and dioxin-like activities.