Peruvian potato cyst nematode populations were analysed to assess both their inter- and intraspecific similarities. ITS--RFLP and two satellite DNA sequences were used as taxonomic tools. Both techniques have confirmed that the Peruvian populations have as their closest relatives the European Globodera pallida, despite the detection of clear differences that prevents us from assigning these South American populations unambiguously to any Globodera species. A more precise study of the variability of these Peruvian populations was investigated and they were compared with the imported European populations using protein (2-DGE) and DNA (RAPD) datasets. The clear distinction between the Peruvian and the European populations was confirmed and, inside each group, no correlation was found between the pathotype classification and the observed clustering of the populations. Surprisingly, while RAPDs revealed a higher variability in the Peruvian group than in the European one, some characteristic proteins were found by 2-DGE in some European populations, whereas it was impossible to find any in the Peruvian populations. It is concluded that the primary founders of the European populations may have an origin other than that of the Peruvian populations involved in this study.