Introduction: Polydactyly has been recognized as an autosomal dominant illness since centuries, nevertheless, its inheritance remain unclear until our days. It has different clinical characteristics in different populations according their ethnic origin, even more, the gene responsible has been mapped to different chromosomal regions in different families. Aim: The purpose of this study is to determine the clinical characteristics, prevalence and gene penetrance of polydactyly in a Chilean Hospital, member of the ECLAMC (HCUCH, Hospital Clinico of University of Chile). Patients and Methods: We studied every polydactyly case detected in the 37.008 newborns occurred from1991 until 2006 at the HCUCH. Results: We found 92 cases of polydatyly, 28 of them were associated to others congenital malformations. The prevalence at birth of the isolated polydactyly was 1,7 x 1.000 births (13 preaxials and 46 postaxials cases). The polydactyly frequency was higher in male than females, even this predominance didn’t reach statistical significance. The prevalence was similar in hands and foot. The 30,4% of cases had a relative with polydactyly. Based on these familial cases we estimated a gene penetrance of 62,6% for postaxial polydactyly; this high family recurrence agree with a dominant inheritance, with modifier genes. Conclusions: The postaxial polydactyly is the most common. The familial distribution of cases is compatible with an autosomal dominant patron of inheritance with a gene penetrance of 62,6%. The presence of preaxial polydactyly and the absence of relatives affected with this anomaly, suggests the existence of associated malformations in the newborn