A survey of amplified fragment length polymorphism (AFLP) was conducted to examine genetic diversity in 146 individuals of British, native black poplar (Populus nigra subsp. betulifolia) and three individuals considered by collectors to be non-betulifolia poplars. Using two primer pairs, a total of 147 bands were detected of which 82 (56%) were polymorphic in at least one individual. Cluster analysis and principal coordinates analysis of the calculated similarity matrix revealed a low level of genetic diversity, although a loose clustering into five groups could be identified, one of which contained the non-betulifolia individuals. Examination of the spatial distribution of the other four groups (all betulifolia) revealed a general correlation between geographic proximity and genetic similarity. On the basis of the polymorphism observed, it was possible to identify a small number of individual plants which exhibit maximum diversity and might therefore be suitable for inclusion in a replanting programme designed to maintain at least the existing low level of polymorphism observed within British black poplar.