Mycosis fungoides and the Sezary syndrome, together known as the cutaneous T cell lymphomas,1,2 are low grade non-Hodgkin's lymphomas with a mature helper T cell phenotype and monoclonal rearrangements of the T cell receptor genes. They should not be confused with intermediate and high grade non -Hodgkin's lymphomas of T cell origin affecting the skin - which, confusingly, are also sometimes referred to as cutaneous T cell lymphomas. In the United States there are between 500 and 1000 new cases a year - compared with 49 000 new cases of non-Hodgkin's lymphoma3 - and their incidence is increasing. The aetiology of mycosis fungoides and the Sezary syndrome is unknown, though several putative retroviruses and environmental factors have been implicated.1,2 There are also many difficulties in determining treatment because many reviews of published studies do not use a standard staging classification, although a TNM and blood based staging system has been widely adopted in recent years4; many studies do not use standard response criteria and have too few patients to draw meaningful conclusions; and there are few randomised studies comparing different approaches to treatment. Nearly all patients have symptoms from their skin lesions, which may itch and cause pain, infection, bleeding, or disfigurement. Topical treatments, both chemotherapy and radiotherapy, are therefore the mainstay of treatment. Radiotherapy was shown to clear the cutaneous lesions in the …