BACKGROUND & AIMS: Cryoglobulins (circulating immune complexes of polyclonal IgG, monoclonal IgM, and rheumatoid factor) are detected in the circulation of 40% to 60% of patients with chronic hepatitis C virus infection, and cryoglobulinemic vasculitis (CV) is observed in approximately 10% of patients. We aimed to assess the clinical and immune effects of direct-acting antiviral treatment. METHODS: We performed a prospective study of 64 patients with HCV infection with circulating cryoglobulins receiving direct-acting antiviral therapy at a single center in Barcelona, Spain, from January 2014 through April 2016. Patients were classified as having CV (n = 35) or asymptomatic circulating cryoglobulins (ACC, n = 29). Clinical response was considered complete if a patient's Birmingham Vasculitis Activity Score (version 3) was 0, or if all affected organs improved 12 weeks after the end of therapy. A complete immunologic response (CIR) was defined as no detection of circulating cryoglobulins and normalized levels of complement and/or rheumatoid factor. RESULTS: Clinical manifestations of CV included purpura (65%), weakness (70%), arthralgia (31%), myalgia (20%), peripheral neuropathy (50%), and renal involvement (20%). At baseline, patients with CV had significantly higher levels of rheumatoid factor and lower levels of C4 complement than patients with ACC, whereas cryocrits were similar between groups (3.2% vs 2.6%). Overall, 60 patients (94%) had a sustained viral response 12 weeks after therapy. Among patients with CV, the median Birmingham Vasculitis Activity Score (version 3) decreased from 9 (range, 2-31) to 3 (range, 0-12) (P <.001). Twenty-five patients with CV (71%) achieved a complete clinical response. Immune-suppressive therapy was reduced for 4 of 13 patients and withdrawn for 6 of 13. Overall, 48% of patients achieved a CIR. A low baseline cryocrit level (< 2.7%) was the only factor associated with CIR (odds ratio, 9.8; 95% confidence interval, 2.2-44; P =.03). CONCLUSIONS: Viral eradication was associated with clinical improvement in most patients with CV. Markers of immune activation, including circulating cryoglobulins, persisted in 52% of patients with CV or ACC, despite a sustained viral response 12 weeks after therapy. A longer follow-up period after viral eradication might be necessary to ensure a normal immune response.