Purpose To evaluate the risk of endometrial cancer and/or endometrial hyperplasia with atypia in asymptomatic postmenopausal women with endometrial thickness >= 11 mm. Methods Results Systematic review of literature using database search (PubMed and Web of Science) of articles published between January 1990 and December 2016 evaluating the correlation between endometrial thickness as measured by transvaginal ultrasound (double layer) and histopathological findings in asymptomatic postmenopausal women, using the following terms: "endometrial thickness," "postmenopausal," "postmenopause," and "asymptomatic." Inclusion criteria were prospective or retrospective studies of more than 150 cases that provided information on endometrial thickness and its correlation with histopathological data. Studies that included patients with hormone replacement therapy, tamoxifen, or aromatase inhibitors were excluded. The overall relative risk (RR) for EC/EHA was calculated, stratifying the patients into two groups according to endometrial thickness (<11 mm and >= 11 mm). Heterogeneity was assessed by calculating I-2. The search identified 289 studies. After exclusions, nine articles that met all the inclusion criteria were included, comprising data from 4751 women. The prevalence of endometrial cancer and/or endometrial hyperplasia with atypia was 2.4%. The relative risk of endometrial cancer and/or endometrial hyperplasia with atypia in the >= 11 mm group was 2.59 (95% CI: 1.66-4.05). High heterogeneity was observed between studies (I-2: 57.3%, P = .016). Conclusions Overall the risk for EC/EHA was 2.6 times greater in women with ET >= 11 mm vs women with ET 5-10 mm, although there was significant heterogeneity in estimates across studies.