Purpose: To assess the occurrence and the associated risk factors for nocturia among middle-aged and elderly people from public health centers in southern Taiwan. Materials and Methods: Data were part of our previous cross-sectional study which used a self-administered questionnaire for the assessment of lower urinary tract symptoms. A total of 1011 responders who were at least 40 years of age were enrolled from any of four local public health centers for any reason in Pingtung County, Taiwan. Nocturia, as a dependent variable, was defi ned as two or more episodes per night. Covariables included age, gender, and chronic illnesses (obesity, hypertension, diabetes, cardiovascular disease, and stroke). Multivariate logistic regression was applied to determine the risk factors associated with nocturia. A p-value of less than 0.05 was considered statistically signifi cant. Results: About 38.1% (385/1011) of the participants reported having nocturia 2 episodes/night, and the occurrence of nocturia increased with advanced age. More than half (51.2%, 197/385) participants with nocturia perceived at least "a bit of a problem" on the sleep quality. The multivariate logistical regression showed that the independent risk factors for nocturia were age (OR:1.06, CI:1.05-1.08), hypertension (OR:1.58, CI:1.16-2.16) and diabetes (OR:1.59, CI:1.03-2.45) and obesity (OR:1.47, CI:1.02-2.10), while a borderline effect on nocturia was produced by cardiovascular disease (OR:1.66, CI: 0.98-2.79) and stroke (OR:2.75, CI:0.88-8.64). Conclusions: Several chronic illnesses coexisted with nocturia. Health care providers need to be aware of an increased risk of nocturia among people with certain chronic illnesses, and provide appropriate health care.