Acquired bilateral nevus-of-Ota-like macule (ABNOM) is a common skin dyspigmentation in Asian females. Although its clinical characteristics are well defined, its epidemiology and pathogenesis remain unclear. A large population-based cross-sectional study was conducted to determine the prevalence and risk factors of ABNOM. A total of 8,680 subjects (ages ranging from newborn to 99 years old; 54% female) were selected from urban areas in Shanghai, China, using a multistage sampling method. All participants (response rate=97%) were interviewed and examined for the presence of various pigmentary disorders by board-certified dermatologists. ABNOM was found in 2.5% of the study population (0.5% of males and 4.2% of females), and 90% of cases observed were female. In females, prevalence rose after the age of 15 years and sharply declined after the age of 50 years, with nearly half of the cases observed within ages 45-55 years (prevalence=8.5%). Age, contraceptive use, and sun exposure were independently associated with ABNOM. Women with ABNOM were less likely to have facial nevomelanocytic nevi and seborrheic keratoses. These findings indicate that sex hormone alteration and UV exposure may independently have an important role on the pathogenesis of ABNOM.