We revealed that the C-type natriuretic peptide (CNP) and its receptor guanylyl cyclase-B (GC-B) system is a potent and physiological stimulator of endochondral bone growth by using transgenic and knockout mice. In humans, one form of skeletal dysplasias, acromesomelic dysplasia, type Maroteaux, was reported to be caused by loss of function mutations in the GC-B gene. Further studies are needed for clarifying the patho-physiological roles of the CNP/GC-B system on human skeletal dysplasias. Moreover, we will have to translate this effect of the CNP/GC-B system on endochondral bone growth into skeletal dysplasias.