DINTO is an OWL ontology that systematically organizes all drug-drug interaction (DDI) related information. Drug-drug interactions (DDIs) form a significant risk group for adverse effects associated with pharmaceutical treatment. These interactions are often reported in the literature, however, they are sparsely represented in machine-readable resources, such as online databases, thesauri or ontologies. DINTO is an ontology that describes and categorizes DDIs and all the possible mechanisms that can lead to them (including both pharmacodynamic and pharmacokinetic DDI mechanisms).