The targeting potential of three different monoclonal antibodies (MAbs) was assessed in patients with ovarian cancer. HMFG1, OC-125 and H17E2 labelled with ¹¹¹In or ¹²³I were evaluated prospectively for their ability to localize ovarian tumour. Forty two patients with ovarian cancer, aged 40-78 years (median=58 years) were studied using OC-125 (n=9), HMFG1 (n=11) and H17E2 (n=22). Imaging data were compared with the CT and the surgical findings. Presence of tumour was confirmed in 35/42 (83%) patients (8/9 OC-125, 10/11 HMFG1 and 17/22 H17E2) and correlated well with the conventional radiology diagnostic methods. One patient with a negative H17E2 scan and a large abdominal mass detected at laparotomy revealed a PLAP-negative tumour on immunohistochemistry. Scintigraphy revealed the presence of active disease, confirmed by laparotomy/laparoscopy in 6/8 patients considered to be in clinical remission. The sensitivity of the method was high enough and the diagnostic contribution of this approach should be further evaluated.