The purpose of this study is to evaluate the safety and tolerability of FG-3019, a therapeutic antibody designed to block the pro-fibrotic activity of connective tissue growth factor (CTGF). CTGF triggers the production of collagen and fibronectin, which cause scarring and thickening of the lungs. Approximately 18 to 27 males and females, 21 to 80 years of age with a diagnosis of idiopathic pulmonary fibrosis (IPF) will be enrolled in this study. The duration of the study is approximately one month, during which patients will receive a single infusion of FG-3019. In addition, there will be two follow-up visits 6 and 12 months after receiving the study drug.