Lichen sclerosus (LS) is a chronic localized lymphocyte-mediated dermatosis of genital skin with a presumed autoimmune origin. LS is characterized by localized dense lymphocytic tissue infiltrates, vasculitic processes and extensive tissue destruction. The lymphocytic infiltrate of LS biopsies contains between 1.4% and 21% of T-cells with monoclonally rearranged T-cell receptor gamma-chain gene, and the immunophenotype is dominated by B-cells, CD4-positive T-cells and antigen-presenting dendritic cells. Antigen-driven selection of T-cells and restricted T-cell receptor usage reflects prolonged exposure of the host immune system to a local (putative LS-associated) antigen. It is presently unclear at which time point in the evolution of LS the T-cell clones emerge. All investigators of LS agree on the non-neoplastic nature of the infiltrate. However, a small percentage of LS patients show serological (systemic) evidence of T-cell immune deficiencies. The lack of long-term follow up of patients with known monoclonally rearranged T-cell receptor gamma-chain gene in their LS biopsies, however, defers a final judgement on the clinical significance of our observations.