A comprehensive synopsis of the welfare of captive, wild (ie non-domesticated) animals in travelling circuses is missing. We examined circus animal welfare and, specifically, behaviour, health, living and travelling conditions. We compared the conditions of non-domesticated animals in circuses with their counterparts kept in zoos. Data on circus animals were very scarce; where data were absent, we inferred likely welfare implications based on zoo data. Circus animals spent the majority of the day confined, about 1-9% of the day performing/training and the remaining time in exercise pens. Exercise pens were significantly smaller than minimum zoo standards for outdoor enclosures. Behavioural budgets were restricted, with circus animals spending a great amount of time performing stereotypies, especially when shackled or confined in beast wagons. A higher degree of stereotyping in circuses may be indicative of poorer welfare. Inadequate diet and housing conditions, and the effects of repeated performances, can lead to significant health problems. Circus animals travel frequently and the associated forced movement, human handling, noise, trailer movement and confinement are important stressors. Although there is no conclusive evidence as to whether animals habituate to travel, confinement in beast wagons for long timeperiods is a definite welfare concern. Circuses have a limited ability to make improvements, such as increased space, environmental enrichment and appropriate social housing. Consequently, we argue that non-domesticated animals, suitable for circus life, should exhibit low space requirements, simple social structures, low cognitive function, non-specialist ecological requirements and an ability to be transported without adverse welfare effects. None of the commonest species exhibited by circuses, such as elephants and large felids, currently meet these criteria. We conclude that the species of non-domesticated animals commonly kept in circuses appear the least suited to a circus life.