Appendix I lists species that are the most endangered among CITES-listed animals and plants (see Article II, paragraph 1 of the Convention). They are threatened with extinction and CITES prohibits international trade in specimens of these species except when the purpose of the import is not commercial (see Article III), for instance for scientific research. In these exceptional cases, trade may take place provided it is authorized by the granting of both an import permit and an export permit (or re-export certificate). Article VII of the Convention provides for a number of exemptions to this general prohibition.
Appendix II lists species that are not necessarily now threatened with extinction but that may become so unless trade is closely controlled. It also includes so-called "look-alike species", i.e. species whose specimens in trade look like those of species listed for conservation reasons (see Article II, paragraph 2 of the Convention). International trade in specimens of Appendix-II species may be authorized by the granting of an export permit or re-export certificate. No import permit is necessary for these species under CITES (although a permit is needed in some countries that have taken stricter measures than CITES requires). Permits or certificates should only be granted if the relevant authorities are satisfied that certain conditions are met, above all that trade will not be detrimental to the survival of the species in the wild. (See Article IV of the Convention)
Appendix III is a list of species included at the request of a Party that already regulates trade in the species and that needs the cooperation of other countries to prevent unsustainable or illegal exploitation (see Article II, paragraph 3, of the Convention). International trade in specimens of species listed in this Appendix is allowed only on presentation of the appropriate permits or certificates. (See Article V of the Convention)
Species may be added to or removed from Appendix I and II, or moved between them, only by the Conference of the Parties, either at its regular meetings or by postal procedures (see Article XV of the Convention). But species may be added to or removed from Appendix III at any time and by any Party unilaterally (although the Conference of the Parties has recommended that changes be timed to coincide with amendments to Appendices I and II).
The names of species in the Appendices may be annotated to qualify the listing. For example, separate populations of a species may have different conservation needs and be included in different Appendices (e.g. the wolf populations included in Appendix I are only those of Bhutan, India, Nepal and Pakistan, whereas all others are included in Appendix II). Such specifications can appear next to the species name or in the Interpretation section. For this reason, the Appendices should always be consulted alongside the Interpretation with which they are presented.