Applications handed in for experimental release (Part B) or commercial release of a genetically modified (GM) plant, require information for risk assessment, including molecular data. In carrying out its assessments, the SBB has noted a variation among dossiers in both quantity and quality of the molecular data. In order to provide applicants with practical guidelines concerning the molecular genetic data for Part B and Part C releases, guidelines on molecular characterisation were prepared. The objectives were to provide guidance on (i) the extent of the molecular data required for GM plants and (ii) the scientific rigour with which this should be done. These guidelines may develop further in function of the biotechnological developments and regulatory demands.