IgG2 deficiency has been recently associated with the appearance of vasculitis. None of the 42 patients with IgG2 deficiency whom we studied has a history of vasculitis. We have also studied 56 patients with vasculitis, and found four of them with IgG2 levels below the normal range for their age. As a group, the vasculitis patients did not differ in the incidence of low IgG2 levels from a normal population. Three of the four vasculitis patients with low IgG2 levels had a Henoch-Schonlein syndrome, and the association between both features was statistically significant.