We report a new disorder that we have called genochondromatosis. Four patients from the same family with the characteristic localisation of chondromatosis (clavicle, upper end of humerus, and lower end of femur) were investigated. The favourable course, the dominant transmission, and previous publication of similar cases confirm the uniqueness of this new entity. The chondrodysplasias with disorganised development of cartilage are far from being completely understood. Recently, several disorders within this group have been well defined, including metachondromatosis and spondyloenchondroplasia, but there still remain numerous clinical subgroups that are very difficult to classify.