We describe an unusual case of pulmonary involvement by mycosis fungoides in a 31-year-old woman. Disseminated disease had developed despite cutaneous irradiation and systemic combination chemotherapy. Microscopy of biopsied tumour deposits in the lung showed a polymorphous, angiocentric lymphoid infiltrate, including atypical cells with convoluted nuclei which displayed a T-cell phenotype. Numerous epithelioid granulomas were also present. These histological appearances represent an unusual pattern of pulmonary involvement by disseminated mycosis fungoides.