There are several definitions of standard. The sort of standard we are considering here is measurable or describable in sufficient detail to make comparison possible. It is agreed and recognized by all, at least generally; it is a fixed reference point to use in comparisons. Some standards are legally enforceable; many are internationally recognized, or are international standards themselves. For standards to survive in use they should meet certain general criteria: predictability, measurability, relevance, technical and economical feasibility, enforceability, and social/cultural/ academic acceptability. Without exception, these criteria can be applied to the use of standards in conservation, the subject of this paper.