Two premenopausal women presented with endometrioma and slightly elevated CA 125 plasma levels (42.5 and 39.0 U/ml). After initial evaluation, both patients had an episode of sudden onset of pelvic pain with rapid resolution after a few hours. During the pain episode, CA 125 plasma levels were similar to the initial evaluation (41.7 and 40.3 U/ml), while 12 h after resolution of the pain, very high levels were measured in both patients (630 and 575 U/ml). The absence of tubal abnormalities and the negative peritoneal fluid cultural evaluation demonstrated by laparoscopy suggested a retrospective clinical diagnosis of partial ovarian torsion with sudden spontaneous untwisting. Therefore, an abnormal elevation of CA 125 plasma levels in patients with benign adnexal masses may be correlated with episodes of partial ovarian torsion with subsequent detorsion.