Different approaches (including association studies) have recently been adopted for the functional characterization of allelic variation in plants and to identify sequence motifs affecting phenotypic variation. We propose the term 'functional markers' for DNA markers derived from such functionally characterized sequence motifs. Functional markers are superior to random DNA markers such as RFLPs, SSRs and AFLPs owing to complete linkage with trait locus alleles. We outline the definition, development, application and prospects of functional markers.