During the last few years, the diagnosis of cutaneous lymphoma has benefited from new techniques. Immunohistochemical staining helps in the early diagnosis of mycosis fungoides and has contributed to a better characterization of non-epidermotropic lymphomas. The possibility of immunohistochemical staining on paraffin-embedded sections has facilitated its execution. CD 30 antigen expression seems to have a prognostic value for nonepidermotropic giant T-cell lymphomas. The prognostic value of expression of one of the two types of T-cell receptors for the antigen, alpha/beta or gamma/delta, remains to be established. The anti-V region antibodies may constitute a marker of clonality for some T-cell lymphomas and demonstrate that in some cases of mycosis fungoides the infiltrate is strictly intraepidermal. Genotype determination represents an advance in the diagnosis of certain nonepidermotropic lymphomas which cannot be characterized on the basis of immunohistochemical data alone. On the other hand, the Southern blot test has been unable to solve the difficult problem of the early diagnosis of mycosis fungoides. Polymerase chain reaction is a novel and very promising technique the usefulness of which remains to be determined. It can already be predicted that it will confront the clinicians with a problem: the significance of demonstrating very small clonal populations. A better knowledge of various cytokines makes it easier to understand the course of cutaneous lymphomas. Finally, advances in molecular biology techniques in the field of retroviruses suggest that defective retroviruses might be the cause of some cutaneous lymphomas.