Paraneoplastic cerebellar degeneration is a rare remote effect of ovarian and breast carcinoma especially, and is characterised clinically by rapidly evolving pancerebellar symptoms. A woman aged 83 developed progressive vertigo, cerebellar ataxia, nystagmus and dysarthria. The cerebrospinal fluid showed slight mononuclear pleocytosis, elevated total protein and IgG concentrations, and oligoclonal bands. A magnetic resonance investigation performed within the first month of symptoms was normal. A left pelvic mass was found, possibly a carcinoma of the colon or the left ovary. Cancer antigen 125 was elevated in the serum and antibodies against Purkinje cells (anti-Yo antibodies) were demonstrated in the serum and cerebrospinal fluid. These results suggested a carcinoma of the ovary as primary site of cancer. Autopsy revealed a left ovarian adenocarcinoma and marked loss of Purkinje cells in the cerebellum. The case illustrates that anti-Yo antibodies may serve as a marker not only for paraneoplastic cerebellar degeneration, but also for the nature of the neoplasm that caused it.