Atypical hemolytic uremic syndrome (aHUS) is a rare, chronic, life-threatening disease due to complement dysregulation. The use of early-onset plasma therapy is recommended, but optimal long-term treatment regimen is not well defined. Eculizumab, a monoclonal humanized anti-C5 antibody, has shown success in patients with aHUS. We report a 7-year-old girl with aHUS associated with factor H mutations successfully treated with eculizumab. Weekly plasma infusion (PI) of 25-30 ml/kg with short-term intensified PI during aHUS exacerbations was effective for 4.3 years. Progressive mild renal failure (stage 2) was attributed to chronic glomerular lesions. Subsequently, she exhibited aHUS exacerbation unresponsive to intensified PI. Eculizumab was initiated at 600 mg, resulting in immediate and complete inhibition of terminal complement activation. During the week following treatment, we observed a complete reversal of aHUS activity. She has been receiving 600 mg eculizumab every 2 weeks for the last 12 months. She had no aHUS exacerbation, and serum creatinine level returned to normal. In this patient, eculizumab led to control of PI-resistant aHUS exacerbation and chronic microangiopathic hemolytic activity. Clinical trials are ongoing to assess the safety and efficacy of this drug in the management of aHUS.