The aims of this study were to investigate the prevalence of nocturia among adults residing in the Matsu area of Taiwan, and to examine the association of this condition with sociodemographic and health characteristics. Between October 2002 and February 2003, all adults older than 30 years residing in the Matsu area were invited to participate in a health awareness campaign. A total of 1706 adults aged 30 to 91 years completed the study survey. Among them, 16.8% reported nocturia with > or = 2 voids per night. The prevalence of nocturia increased with age from 8.4% in the 30-39 years age group to 30.9% in the > or = 70 years age group (p < 0.001). No significant difference of nocturia prevalence was found between men and women. In addition to age, diabetes (odds ratio, 2.5; 95% confidence interval, 1.4-4.2) was also independently associated with nocturia. This study suggests the importance of nocturia as a health problem and the need for greater awareness and treatment.