Vasculitis may accompany rheumatoid arthritis. One must distinguish between vascular involvement associated with the pathogenesis of rheumatoid arthritis, isolated digital vasculitis, and the syndrome of clinical rheumatoid vasculitis. The cause of clinical rheumatoid vasculitis is unknown. High titers of rheumatoid factor, cryoglobulins, diminished circulating complement, an increased prevalence of HLA-DR4, and the pathologic findings suggest an immune etiology. However, similar, but perhaps less pronounced, abnormalities occur in uncomplicated rheumatoid arthritis, and these findings are not universal in complicating vasculitis. Classic cutaneous clinical manifestations include ischemic ulcers, digital gangrene, and palpable purpura. Mononeuritis multiplex is another classic presentation of rheumatoid vasculitis. Small digital infarctions may accompany other manifestations in clinical vasculitis or may occur alone as isolated digital arteritis, in which case the prognosis is relatively favorable. Weight loss, pleuritis, pericarditis, ocular inflammation, splenomegaly, hepatomegaly, and Felty's syndrome have also been reported in association with rheumatoid vasculitis. Although renal involvement has been considered unusual in rheumatoid vasculitis, several studies suggest that this may be more common than previously recognized. Ideally, a biopsy or an angiogram confirms the diagnosis of rheumatoid vasculitis, but often the diagnosis rests upon the clinical picture. In general, blind biopsies are not helpful, although one series indicated that a blind rectal biopsy may be an exception to this rule. An elevated erythrocyte sedimentation rate, increased C-reactive protein level, anemia, thrombocytosis, hypoalbuminemia, and a positive rheumatoid factor are common laboratory findings. Leukocytosis, hypergammaglobinemia, leukocytopenia, an elevated creatinine level, and minimal abnormalities of the urinary sediment also occur in patients with rheumatoid vasculitis. However, these abnormalities overlap in patients with uncomplicated rheumatoid arthritis, and their role in distinguishing rheumatoid vasculitis from uncomplicated rheumatoid arthritis is limited. Other immunologic tests have no established clinical role in diagnosing rheumatoid vasculitis. Therapy depends upon the clinical manifestation of rheumatoid vasculitis. Uncomplicated rheumatoid arthritis deserves appropriate therapy, and general attention to nutrition, cessation of tobacco, and control of blood pressure are indicated for all patients. Isolated digital vasculitis generally requires no more than the usual treatment for uncomplicated rheumatoid arthritis. Appropriate dermatologic management is indicated for ischemic ulcers. Most clinical experience in managing more symptomatic rheumatoid vasculitis has focused on glucocorticosteroids, D-penicillamine, and cytotoxic immunosuppressive drugs.(ABSTRACT TRUNCATED AT 400 WORDS)