To investigate the epidemiologyical characteristics of polydactyly. The method of Hospital-based surveillance within Chinese Birth Defects Monitoring Network (CBDMN) was adopted. All perinatals (from 28 weeks of gestation to a period of 7 days after birth) in the participating hospitals were investigated from 1996 to 2000. A total of 2097 cases were identified in 2218616 perinates, the prevalence was 9.45 per 10000. The prevalence of male was significantly higher than the female's. The urban prevalence was 9.60 per 10000, and the rural prevalence was 9.05 per 10000. Significant difference and increasing time trend were observed in annual prevalence rate during 1996-2000. Of the 2097 cases, 1853 (88.4%) were in the isolated form, and the rest (11.6%) of them were combined with other defects. Among 1942 perinatals affected by polydactyly, 679 (34.96%) cases occurred in the left limbs, 886 (45.62%) cases occurred in the right limbs, and 377 (19.41%) cases occurred bilaterally. The prevalence rates of polydactylies in Chinese perinatals show male predominance and geographic variations. Most of the polydactyly cases were in the from of single defect; however, those accompanied by other defects had a higher perinatal fatality rate.