Between 1972 and 1980 a histological diagnosis of vasculitis was made on 80 patients from a district general hospital. These were divided into a polyarteritis nodosa (PAN) group, a rheumatoid vasculitis (RV) group and a heterogeneous group of other vasculitides. There was considerable overlap between the clinical and laboratory features in the three groups. Non-specific symptoms (fever and myalgia), leucocytosis and eosinophilia were the most useful features for distinguishing PAN from the other two groups. Hepatitis B infection was rare (two patients) and hypocomplementaemia was a feature of RV but not of PAN. The overall mortality was similar in each group. However, in PAN deaths due to vasculitis were more common within six months of diagnosis. Features associated with a poor prognosis were renal impairment, cutaneous and intestinal vasculitis in PAN; and neuropathy, weight loss and histological evidence of vasculitis at rectal biopsy in RV. Cytoxic drugs combined with corticosteroids were associated with an improved prognosis compared with corticosteroids alone in the PAN group. Pulmonary involvement was associated with less severe renal disease but with a six month mortality similar to that in the whole PAN group. Systemic vasculitis is not uncommon in a district general hospital population. The overlapping clinical and laboratory features in different vasculitic diseases stress the problems in classification between PAN and other groups. Patients with systemic disease complicated by necrotizing arteritis have a severe, life threatening disease which may respond to aggressive cytotoxic therapy.