Cytokines are known to alter a number of vascular tissue cell functions. The aim of this retrospective study was to determine serum cytokine levels in patients with vasculitis and to analyse the possible relation to the severity of the disease. Tumour necrosis factor alpha (TNF alpha), interleukin-1 (IL-1)beta, IL-2, interferon (IFN)- and IFN-gamma were assayed in 33 patients with polyarteritis nodosa (PAN) or Churg and Strauss angiitis (CSA), and three with Wegener granulomatosis (WG). Serum cytokine changes were observed in most patients with active disease, i.e. before treatment was started. In the majority of patients with PAN or CSA, there was a marked increase in serum IFN-alpha and IL-2 levels, while TNF-alpha and IL-beta levels were moderately elevated. Serum IFN-gamma remained undetectable in all but one of these patients. In patients with WG, serum IFN-alpha and IL-2 levels were also elevated, whereas IL-1 beta, IFN-gamma and TNF alpha levels remained within normal limits. In paired samples of patients with PAN, IFN-alpha and IL-2 levels were significantly higher before than after treatment. These preliminary data suggest that a particular pattern of cytokine changes is associated with vasculitis and that cytokines might be involved in the pathogenesis of PAN/CSA and WG. Prospective studies are warranted to determine whether cytokines could be considered for the monitoring of disease activity and therapy.