Objective: To assess the natural history of benign appearing purely solid ovarian lesions in asymptomatic postmenopausal women. Methods: Retrospective observational cohort study comprising 99 women (mean age, 58.2 years, ranging from 50 to 77 years) diagnosed as having a purely solid ovarian lesion at transvaginal ultrasound between April 2001 and October 2015. Inclusion criteria were as follows: asymptomatic postmenopausal women with a well-defined purely solid ovarian lesion with International Ovarian Tumor Analysis color score 1 or 2, without ascites and/or signs of carcinomatosis. Clinical, sonographic, biochemical (CA-125), and histologic data (in case of surgery) were retrieved for analysis. Patients who were managed conservatively were assessed by transvaginal sonography every 6 months for a minimum of a year. In case of bilateral lesions we used the largest one for analysis. Results: Five women (5.1%) had bilateral lesions. Mean size of the lesion was 2.9cm (range, 1.0-7.8 cm). Most lesions were homogeneous (96.0%). Acoustic shadowing was present in 59.6% of cases. International Ovarian Tumor Analysis color score was 1 in 77.8% and 2 in 22.2% of the cases, respectively. Median CA-125 was 10.8 IU/mL (range, 3.0-403.0 IU/mL). Forty-two women underwent surgery after diagnosis (histologic diagnoses were as follows: fibroma (n = 26), fibrothecoma (n = 5), dermoid (n = 3), Brenner tumor (n = 3), endometrioma (n = 2), thecoma (n = 1), primary invasive cancer (n = 2). One case of invasive cancer CA-125 was 403.0 IU/mL and in the other case CA-125 was 6.0 IU/mL. They both were stage 1. Fifty-seven women were managed with serial follow-up. With a median follow-up time of 36 months (range, 12-142 months) all these lesions had no change and women remain asymptomatic. Considering all 99 cases the risk of malignancy is 2% (95% CI, 0.1-7.5). Conclusions: The risk of malignancy of benign appearing purely solid adnexal masses in asymptomatic postmenopausal women is low. Conservative management of these lesions might be an option.