Pharmaceutical manufacture is one of the most tightly legislated industries today. The industry is constantly challenged to meet the rising standards of manufacturing quality and safety through rigorous regulatory requirements As a consequence, ensuring regulatory compliance and managing a myriad of validation documents constitutes a major informatics challenge. This study addresses this challenge by developing an ontological infrastructure to support decision making in regulatory compliance The proposed ontological informatics system. called OntoReg, is integrated with a reasoner and a rule engine through a Java integrated development environment The system is demonstrated through industrial case studies based on regulation examples taken from the Eudralex Guide 2007. (C) 2009 Elsevier Ltd All lights reserved