We investigated clonal diversity within patches of Ilex leucoclada and genetic variation within and among patches using random amplified polymorphic DNA (RAPD) markers in a 1-ha plot within an old-growth beech forest. We found 38 patches that exhibited a clumped distribution in the middle of the plot. We identified a total of 166 RAPD phenotypes among the 215 stems sampled from 27 patches that were completely within the plot. The population showed high clonal diversity within patches (mean number of genets relative to number of stems = 0.79; mean Simpson's D= 0.89). Variation in RAPD phenotypes among patches was highly significant (ΦST in the molecular variance analysis = 0.316, P < 0.001), indicating genetic differentiation among patches. Pairwise genetic distances, ΦST, among patches did not correlate with geographical distances among patches. The cluster analysis based on the genetic distances showed few clear clusters of patches, indicating no spatial genetic structure among patches. High levels of clonal diversity both within patches and within the population may be explained by multiple founders, seedling recruitment during patch-formation, and somatic mutation. The significant genetic differentiation among patches may be caused by separate founding events and/or kin structuring within patches.