We have observed a distinct form of "crossed" polysyndactyly in 6 generations of a family with 5 affected persons, all males. The polydactyly is postaxial in the hands and preaxial in the feet. Syndactyly in the hands is observed in some relatives, while syndactyly in the feet is present bilaterally in all affected relatives. This seems to be an autosomal dominant trait with male to male transmission over 3 generations by examination and an additional 3 generations by history. This form of polysyndactyly could not be readily categorized by the existing classification by Temtamy and McKusick [1978: BD OAS XIV 6:363-392]. We review and expand the present classification of polydactyly and syndactyly syndromes.