We estimate penetrance for symptomatic tumours and elucidate genotype-phenotype correlations in a large cohort of <i>SDHB/SDHC</i>/<i>SDHD</i> mutation carriers.<h4>Methods</h4>A retrospective survey of 1832 individuals referred for genetic testing due to a personal or family history of phaeochromocytoma/paraganglioma. The gene discussed is SDHD; the disease is paraganglioma.