The present invention relates to the identification of biological markers of ovarian cancer. Specifically, cancer-associated autoantibodies to ANXA1, ARP3, SAHH, SERPH, ARAP1, OTUB1, ATP1A1, UBA1, and CFAH have been identified in subjects with early stage ovarian cancer. These autoantibodies can be utilised for a range of purposes including methods for detecting ovarian cancer, methods for screening for early stage ovarian cancer, and methods for assessing treatment response as well as disease progression and recurrence. The autoantibodies also represent prognostic markers of ovarian cancer development.