Summary : This teaching module has been developed as a tool for providing regulators with practical training the environmental safety assessment of transgenic plants. The concepts of risk assessment as discussed in this text do not reflect any one country's regulatory approach, but rather have been modelled after international consensus documents such as those produced by the Organization for Economic Cooperation and Development (OECD), the World Health Organization (WHO) and the Food and Agriculture Organization (FAO) of the United Nations. In order to provide some indication of the types of data usually presented in support of an environmental safety evaluation, as case study using genetically engineered maize (Zea mays) event MON 810 (trade name YieldGard) and its progeny has been developed. The content of the study includes excerpts from applications for environmental release submitted to regulatory authorities in the European Union, the United Kingdom (UK), Japan and the United States (US).