The Federal Highway Administration 100-Year Coating Study was initiated in August 2009 to search for durable coating systems at a reasonable cost. The objective of the study was to identify and evaluate coating materials that can provide 100 years of virtually maintenance-free service life for steel bridges. Selected coating systems included three three-coat systems, four two-coat systems, and a single-coat system of high-ratio calcium sulfonate alkyd. All coating systems were evaluated under accelerated laboratory testing and three outdoor exposure conditions, namely natural weathering and natural weathering with salt spray in McLean, VA, and outdoor testing at the Golden Gate Bridge in San Francisco, CA. One design innovation was the employment of 18- by 18-inch large test panels that contained welding joints and angle attachments using bolts and nuts to closely simulate realistic conditions that are encountered in bridges in the field. This report presents results of performance evaluation of the eight coating systems.