This is a randomized, double-blind, placebo-controlled trial designed to assess the efficacy and benefits of pravastatin therapy in adults with ADPKD by evaluating 1) kidney volume as measured by kidney magnetic resonance imaging (MRI); 2) renal blood flow as measured by kidney magnetic resonance angiography (MRA); 3) kidney function as assessed by Glofil-125; 4) plasma and urine protein markers that will allow a better understanding of how pravastatin works in ADPKD; and 5) blood vessel stiffness as measured by carotid-femoral pulse wave velocity. These parameters will be measured at baseline and after 2 years of pravastatin or placebo treatment in 150 patients with ADPKD.