Genetic studies of hereditary paraganglioma tumors could increase the understanding of the biology of these fascinating tumors, with important clinical implications for diagnosis and treatment. This article focuses on the genetics of paraganglioma tumors, with limited reference to their general morphologic and clinical aspects. The paraganglioma tumor phenotype is defined. The genetic and physical mapping studies recently performed are summarized--studies that eventually led to the discovery of the gene for hereditary paraganglioma type 1 (PGL1). Finally, future directions stemming from the PGL gene discovery are described.