Data from a study carried out on a group of 18 patients with hypergammaglobulinemic purpura of Waldenström (HPW) followed-up for 3-14 years are reported in this paper. In 11 patients the syndrome was considered to be idiopathic, while in the remaining 7 it was associated with Sjögren's syndrome (SS). A marked (17/1) female prevalence was observed. Purpura was the presenting clinical manifestation in 9 patients, but it occurred at different points during the course of the disease; Raynaud's phenomenon was present in one third of patients. Serum gammaglobulin levels were higher than 2.2 g/dl in all the cases and higher than 3 g/dl in 9 cases. Immune complexes were detected in all patients. A significant serologic finding in our case series was represented by the frequency of anti-Ro (16/16) and anti-La (14/15) antibodies, clearly higher than that reported in SS patients. HLA typing showed a marked increase of B8 and DR3 antigens as well as A1,B8,DR3 haplotype, never reported in other autoimmune diseases. On the basis of serologic and immunogenetic features, HPW seems a clearly distinguishable entity among autoimmune vasculitis.