Telaprevir (TPV) is one of the NS3/4A serine protease inhibitors on the market for the treatment of chronic hepatitis C genotype 1 in combination with peginterferon alpha and ribavirin. Well-documented potential adverse reactions of TPV are hematological, skin, and gastro-intestinal disorders. Until now, there were no conclusive data from clinical trials about renal adverse reactions of TPV. We report here three cases of renal impairment that occurred after a few days of TPV treatment and resolved in about 2 weeks after stopping the drug. Two of the patients were hospitalized because of this serious adverse drug reaction. Therefore, renal impairment seems to be a new adverse drug reaction of TPV and clinicians should be aware of this potentially serious complication of chronic hepatitis C therapy.