Pursuant to article 8(2) of Directive 91/414/EEC in matter of maketing of plant protection products, this Regulation establishes detailed rules as to the implementation of the first stage of the programnme of work to be performed by the Commission in order to gradually examine the active substances the marketing of which may be authorized by Member States under certain conditions. The first stage involves an assessment of the substances listed in Annex I to this Regulation with a view to their p