Two cases of acrodysostosis syndrome in a brother and sister are reported. The parents and other siblings were unaffected. Features of this syndrome include extremely short, broad metacarpals, metatarsals, and phalanges, nasal hypoplasia, short stature, and mental deficiency. Previously published familial cases of acrodysostosis syndrome are consistent with autosomal dominant transmission, whereas the cases reported herein suggest other genetic mechanisms including recessive autosomal transmission, unstable mutation, and germ cell mosaicism, the latter being the most attractive hypothesis.