It is often problematic to diagnose T-cell lymphoproliferative disorders of the skin because of the difficulty in establishing clonality in paraffin-embedded tissue. We used polymerase chain reaction single strand conformational polymorphism (PCR-SSCP) and heteroduplex analysis in paraffin embedded tissue to detect clonal rearrangement of T-cell receptor gamma (TCRgamma) gene in 17 T-cell lymphoproliferative disorders and 6 atypical lymphoproliferative diseases. We used polymerase chain reaction to detect TCR beta gene rearrangement in 8 of 17 cases which did not show TCRgamma gene rearrangement. Jurkat cell lines were used as monoclonal controls. DNA was extracted from 5 biopsies of T-cell lymphomas, 10 biopsies of mycosis fungoides, 2 biopsies of lymphomatoid papulosis, and 6 biopsies of atypical lymphoproliferative lesions. We detected monoclonality in 5 of 5 T-cell lymphoma cases, 2 of 2 lymphomatoid papulosis cases, 6 of 10 mycosis fungoides cases, and 2 of 6 atypical lymphoproliferative disease cases. We conclude that nonradioactive PCR-SSCP for TCR gene rearrangement analysis is a useful adjunct to routine histological and immunophenotypic methods in the diagnosis of cutaneous T cell lymphoproliferative disorders in paraffin embedded tissue.