A 43-year-old man with tumour stage mycosis fungoides developed multiple follicular pustules on the trunk during total-skin electron beam therapy. A potassium hydroxide preparation of the contents of the pustules revealed the presence of Demodex mites. The patient was treated with 6% sulphur lotion with rapid improvement of the cutaneous lesions. We believe that this case represents a pustular folliculitis caused by Demodex mites. Immunosuppression associated with mycosis fungoides and its treatment may have resulted in the proliferation of this obligate parasite of the pilosebaceous follicle, and the development of the folliculitis.