Millions of wild mammals are trapped annually for fur, pest control and wildlife management. Ensuring the welfare of trapped individuals can only be achieved by trapping methods that meet accepted standards of animal welfare. At the international level, the assessment of mechanical properties of killing and restraining traps is set out in two documents published by the International Organization for Standardization (ISO). Few traps currently in use have been tested according to the ISO standards and, in addition, new traps have been designed and old traps modified since the publication of the standards. In this paper we review trapping methods used in Europe and North America to see whether they meet the ISO standards and examine ways to improve the welfare performance of traps. In addition, international legislation is assessed to determine whether this ensures a sufficient level of welfare for trapped animals. Finally, trapping practices used in academic research are reviewed. We conclude that many of the practices commonly used to trap mammals cannot be considered humane. Current legislation fails to ensure an acceptable level of welfare for a large number of captured animals. New welfare standards for trapping wild mammals need to be established so that in future a minimum level of welfare is guaranteed for all trapped individuals.