Computer prediction of chemical toxicity is becoming important in submissions to regulatory authorities for the approval of new pharmaceuticals and other chemical products. To reach a decision about the potential risks associated with the toxicity of a chemical, an individual human or a committee takes into account all available information. Some information may be corroborative, some contradictory, some irrelevant and misleading. Computer reasoning makes it possible to support decision-making by drawing together diverse information and presenting judgments about it with supporting explanations and justification.