Chemical process industries such as oil refineries, fertiliser plants, petrochemical plants, etc., which handle hazardous chemicals, are potential targets for deliberate actions by terrorists, criminals and disgruntled employees. Security risks arising out of these threats are real and must be assessed to determine whether the security measures employed within the facility are adequate or need enhancement. The essential components of security management programme include security risk assessment, security countermeasures, and emergency response. Security risk assessment can be carried out qualitatively by threat analysis, vulnerability analysis and developing Security Risk Factor Table. It is recognised that many of the conventional safety and security measures have to be modified in light of enhanced nature of threat. Two case studies: one of a fertiliser plant and the other on a refinery has been presented in this work to show the application of ideas. This work will be useful to the safety and security professionals, workers/managers of a chemical industry or any other individual interested to counter the hazard of terrorism.