Genetic counselling in the confusing group of primary bone dysplasias requires special care. Full radiographic and clinical assessments are essential for a firm diagnosis to be reached; even so, some cases remain undiagnosed. In such a situation, one must be guided by the pedigree pattern of the individual family. Most types follow Mendelian inheritance, but for an isolated case it is often impossible to distinguish between a new dominant mutation and autosomal recessive inheritance on clinical (and radiological) features. Few clinicians see many cases of bone dysplasia, so it is unreasonable to expect familiarity with every type. Pooling experience is of great help; bone dysplasia groups in different centres, and those that cooperate on a national or supranational basis, can be of great value; they involve radiologists, orthopaedic surgeons and paediatricians, as well as geneticists. Within the United Kingdom the Skeletal Dysplasia Group fulfils this purpose. The discussion of problem cases at such meetings allows accurate diagnosis and genetic counselling that would not be possible otherwise.