Application of magnesium alloys in vehicles can reduce weight, increase fuel efficiency, and improve vehicle performance. So why aren’t today’s cars and trucks made of magnesium? A long list of technical and commercial challenges introduces barriers to use, and properly addressing all barriers for all components throughout a vehicle would require enormous resources (and may not be ideal anyway). However, there are key components and structures where magnesium provides the greatest potential benefits. Targeting the critical issues of cost, corrosion, and formability for the most promising vehicle applications offers a route towards efficient use of R&D resources and greater likelihood of commercial success. Following a discussion on the state of the art, these applications and challenges are summarized and a discussion of new opportunities is presented.