A patient with paraneoplastic cerebellar degeneration due to anti-Purkinje cell antibodies (anti-Yo) arising from ovarian carcinoma with metastases was treated with three plasmapheresis (PP) series (a total of 22 PP treatments) over one year and was monitored by repeated otoneurological testing, balance tests and clinical investigations. Blood samples for antibody titers were checked on several occasions. Initially there was a weak clinical response and significantly improved test results regarding the caloric response, as well as a possible effect on visual suppression of the vestibulo-ocular reflex after caloric ear irrigation. After the first series of PP treatment, new metastases were found. A half year later there was a progressive course with increasing general symptoms. Serology tests showed continuously high titers of anti-Yo antibody, although somewhat lower after PP. We thus report a minor and short-lived effect of PP, possibly inhibited by the natural course of metastatic disease.