Since 1976, 28 states have repealed or significantly amended their motorcycle helmet laws. The change in legislation was not based on an evaluation of the costs and benefits of such laws. This paper attempts such an assessment by comparing the cost of motorcycle helmets with the medical costs averted due to helmet use using data primarily based on motorcycle crashes in Colorado, Oklahoma, and South Dakota. Nationwide, at least $61 million could be saved annually if all motorcyclists were to use helmets. Helmet law repeals have been observed to lead to a 40 to 50 per cent point reduction in helmet use. The associated additional medical care costs substantially exceed cost savings produced by reduced helmet use. It is estimated that helmet law repeals may produce annually between $16 and 18 million of unnecessary medical care expenditures. Several alternatives to increase motorcycle helmet use are briefly discussed. It is concluded that helmet laws are effective in encouraging helmet use among motorcyclists and will prevent unnecessary medical expenditures as well as unnecessary pain and suffering among injured motorcyclists.