To date, the Chinese clam Anodonta woodiana Lea, native to the Amur and Yangtze river basins, has been reported from three localities in Poland. Since the early 1990s, the species has massively colonised its first Polish locality, i.e. heated lakes near Konin in central Poland. Since 2002 and 2003, the clam has also been found in, respectively, fish ponds near Sieraków (Greater Poland) and the heated channel of the Dolna Odra power station near Szczecin, NW. Poland. In order to estimate the genetic variability of the first, pioneer populations in Poland, 12 enzymatic loci were analysed using starch gel electrophoresis. A. woodiana exhibits a strong genetic variation, as demonstrated by the following parameters of genetic variability for its Polish populations: 66.7–83.3% polymorphic loci, 2.3 alleles on average per locus and 2.6–2.9 per polymorphic locus, an average of 2.53 genotypes per population, and average expected heterozygosity of 0.30–0.35. The results suggest either a massive colonisation by genetically diverse individuals, or a multiple colonisation by founder populations coming from various water bodies. The genetic similarity (Nei) between the populations of A. woodiana is high (0.83 to 1.00), which suggests a strong genetic homogeneity of this species in its first locality in Poland.