To address this question, rat cerebellar slice cultures were incubated with commercial antibodies reactive against three intracellular Purkinje cell proteins, calbindin, calmodulin, and PCP-2 as well as with sera from three ovarian cancer patients exhibiting serum anti-Purkinje cell cytoplasmic antibodies not reactive with Yo antigen (Patients 1, 2, and 3). The gene discussed is CDR2; the disease is ovarian carcinoma.