Simple hepatic cysts are now being diagnosed more frequently with the widespread availability of sonographic imaging. Among the general population, the prevalence was reported to be between 0.1 and 2.5%, more so in women, and more often in the right lobe. We conducted this large scale community-based sonographic screening on simple hepatic cysts to explore the age- and sex-specific prevalence in Taiwan. We also conducted another hospital-based study to record the size of simple hepatic cysts. A total of 3,600 subjects in 8 communities were recruited and 156 simple hepatic cysts in 132 study subjects were detected. The overall prevalence is 3.60%. An increasing prevalence with age is demonstrated, ranging from 0.83% from below the age of 40 up to 7.81% of patients over 60 years old. The sizes of 219 simple hepatic cysts of 167 patients out of the hospital-based 5,893 patients were recorded in detail; 53% of cysts were of a diameter of between 1 and 3 cm, and only 7% were larger than 5 cm.