Anti-tumor antibodies have potential as cancer biomarkers. There is relatively limited identification of anti-tumor antibodies in response to ovarian cancer, compared with studies for other cancers. There is also very limited information on the prevalence of anti-tumor antibodies among ovarian cancer patients. Although most anti-tumor antibodies react with antigens common to both tumor and normal tissue, the anti-tumor response tends to be confined to individuals with ovarian cancer, similar to other cancers. Antibodies to HOXA7, a differentiation antigen, have the highest reported prevalence in ovarian cancer (67%). Antibodies to other ubiquitous antigens including NY-ESO-1, Ep-CAM (epithelial cell adhesion molecule), HSP-90 (heat shock protein 90), and mutated p53 have been identified in ovarian cancer. Anti-tumor antibody specificity reflects the heterogeneity of antigen expression in tumors. Tests based on panels of a combination of anti-tumor antibodies may be more predictive for ovarian cancer, as no single specificity accounts for ovarian tumors. In addition to characterization of anti-tumor antibodies as diagnostic markers, study of anti-tumor antibodies is likely to provide insights into mechanisms of tumor development. There is evidence of antibodies to tumor antigens and of activated T cells, suggesting immune recognition of tumor antigens occurred. Nonetheless, as tumors are not 'rejected', it is likely that there are alterations in the immune system. The basis for tumor growth in the face of immune activity remains to be determined.