This paper uses survey data to determine what costs are imposed upon civilian employers when their military reservist employees are called up for active duty. We find that many employers have no costs and that costs are generally modest. However, a small number of employers have very high costs. Small businesses and first-responder agencies were most likely to have high costs. We consider the options for policies to compensate these employers and conclude that a program of grants targeted at the most severely affected employers would be the best option.