The clinical spectrum and outcome of necrotizing vasculitis were evaluated in a retrospective study in order to assess: (1) the clinical expression and evolution of the disease; (2) the response to several therapeutic approaches based on major events (organ involvement causing disability or death); (3) the immunogenetic background of patients. Sixty-six Greek patients fulfilling the ACR criteria for the diagnosis of vasculitis entered the study. Thirty-seven were diagnosed with Wegener's granulomatosis (WG), 22 with polyarteritis nodosa (PAN) and seven with Churg-Strauss syndrome (CSS). The demographic characteristics of patients with WG and PAN were similar. Cutaneous manifestations, gastrointestinal and peripheral nervous system involvement occurred more often in patients with PAN, whereas pulmonary and upper respiratory tract involvement, renal, ear abnormalities and fever were more frequent in patients with WG. Muscle weakness and asthma were found exclusively in patients with PAN and CSS, respectively, while the presence of classic-antineutrophil cytoplasmic antibodies (c-ANCA) characterized WG patients. Hepatitis B surface antigen (HBsAg) was found in 22% of PAN patients. No significant differences were detected when comparing the PAN and WG groups with respect to the first major event (log-rank P = 0.50) with and without potential confounders (age, gender, therapy or c-ANCA). For WG patients, a statistically significant difference was found on different routes of administration of cyclophosphamide (oral vs pulse) (P = 0.006). Regarding the HLA antigens, an increased frequency of DR1 (26.9% vs 10.3%, P = 0.057) in WG and the absence of DR3 in patients with PAN and CSS were noted. It appears that although the immunogenetic background and the clinical expression of the diseases differ, the response to treatment as well as the evolution and the survival rate of these patients are similar in the two groups.