The international projects for reforming and broadening the scope of the current technical guidelines and standards on thesauri are analyzed. Their aims are to recast the existing standards and guidelines, to adapt them to the new digital environment, and to specify their relation with other vocabulary control tools, making easier their interoperability. In this context, the mission, goals and methodology of the Committee 50’s taskforce on controlled vocabularies of the Spanish Standardization Association (AENOR) are presented. Its mission is promoting in the frame of the AENOR the adaptation of the Spanish standards on thesauri to the new international trends, following the work of the American initiative ANSI/NISO Z39.19-2005, and specially the more complete BS 8723, proposed by the British Standard Institute. According to this last one, the group aims are a) to reunify the standards on monolingual and multilingual thesauri —this is UNE 50106:1990, UNE 50106:1995 Erratum y UNE UNE 50125:1997— in a single one, comprising also the rest of the indexing languages, mainly subject headings, classifications and taxonomies; and b) to clarify the principles and tools among to interconnect the different languages among them and with the emerging field of computer ontologies. To achieve those aims, a working plan in four phases has been established: analysis of the international normative and technological context; cooperation with the British group in the revision of some parts of BS 8723; studying the appropriateness of adopting the norm BS 8723 as a UNE standard; and cooperating with the British group and other interested parts on the promotion of an ISO standard.