Three isozyme systems were analysed in 97 individuals of Taraxacum randomly sampled from 100 m2 of mature sand dune on the north-east coast of England. Ten agamospecies were identified in the sample and another ten occurred nearby. There was no variation found in the sample for tyrosinase or acid phosphatase. For esterase each agamospecies was found to be different and variation was found within five agamospecies. For these variable agamospecies the mean percentage variability was 19 per cent. Variation was found in two out of three offspring families, where the mean percentage variability was 22 per cent. A high level of homozygosity was found among the offspring of mothers heterozygous for tyrosinase.