New psychoactive substances or ‘legal highs’ are widely used by young people. Government attempts to ban the substances have been unsuccessful as they are quickly replaced by new compounds. The substances cannot be detected by current drug screening. This article explores UK policy on legal highs, to draw international comparisons, to establish recommendations for tackling the problem, and to highlight potential implications for UK policy. Policymakers should consider means of regulation including of the sale of legal highs and restrictions on supply. They should examine use of holding measures while harm is evaluated, consider classifying substances based on their potential for harm, and create education programmes on the legal implications of buying legal highs as well as harm caused.