On-farm management of agricultural biodiversity is a complementary strategy to ex situ conservation of genetic resources in genebanks. While there is growing consensus that agricultural biodiversity is being lost from production systems around the world, estimates of the extent of this loss remain crude. Not all farmers are equally involved in the conservation of agricultural biodiversity, and nor should that be the goal of on-farm conservation programs. Both the term and concept of 'custodian farmer' are relatively new in the field of in situ and on-farm conservation of agricultural biodiversity. A custodian farmer should not be seen as the antagonist of a progressive, innovative or entrepreneurial farmer; concepts which have been widely used and discussed in agricultural literature. The method of identification of custodian farmers are evolving and new perspectives are emerging. By definition, custodian farmers tend to maintain a number of crop species and varieties, rich in diversity, compared with fellow farmers in the same community.