The strange association of Dermatomyositis-Polymyositis (DM-PM) and cancer has been known for many years. We present the case of a 57-year-old woman with polymyositis refractory to steroid therapy, in whom extensive investigation finally revealed a squamous cell carcinoma of the vagina. The clinical course of myositis paralleled the course of vaginal cancer, with complete resolution of symptoms after radiotherapy for the malignancy.