OBJECTIVE To determine the sensitivity and specificity of subjective evaluation of gray-scale and Doppler ultrasound findings (here called pattern recognition) when used by experienced ultrasound examiners with regard to making a specific diagnosis of adnexal masses. METHODS Within the framework of a European multicenter study, the International Ovarian Tumor Analysis study, comprising nine ultrasound centers, women with at least one adnexal mass were examined with gray-scale and color Doppler ultrasonography by experienced ultrasound examiners. A standardized examination technique, and standardized terms and definitions were used. Using pattern recognition the examiners classified each mass as benign or malignant and suggested a specific diagnosis (e.g. dermoid cyst or endometrioma). The reference standard was the histology of the surgically removed adnexal tumors. RESULTS A total of 1066 women were included, of whom 800 had a benign mass and 266 a malignant mass. A specific diagnosis based on ultrasound findings was suggested in 899 (84%) tumors. The specificity was high for all diagnoses (range, 94-100%). The sensitivity was highest for benign teratoma/dermoid cysts (86%, 100/116), hydrosalpinges (86%, 18/21), peritoneal pseudocysts (80%, 4/5) and endometriomas (77%, 153/199), and lowest for functional cysts (17%, 4/24), paraovarian/parasalpingeal cysts (14%, 3/21), benign rare tumors (11%, 1/9), adenofibromas (8%, 3/39), simple cysts (6%, 1/18) and struma ovarii (0%, 0/5). The positive and negative likelihood ratios of pattern recognition with regard to dermoid cysts, hydrosalpinges and endometriomas were 68.2 and 0.14, 38.9 and 0.15, and 33.3 and 0.24, respectively. Dermoid cysts, hydrosalpinges, functional cysts, paraovarian cysts, peritoneal pseudocysts, fibromas/fibrothecomas and simple cysts were never misdiagnosed as malignancies by the ultrasound examiner, whereas more than 10% of inflammatory processes, adenofibromas and rare benign tumors including struma ovarii were misdiagnosed as malignancies. CONCLUSIONS Using subjective evaluation of gray-scale and Doppler ultrasound findings it is possible to make an almost conclusive diagnosis of a dermoid cyst, endometrioma and hydrosalpinx. Many other adnexal pathologies can be recognized but not confidently confirmed or excluded.