More long-tailed macaques (Macaca fascicularis) than any other primate are imported into the UK for research, and journey times may be of up to 58 h. Whilst a number of studies have examined the stress associated with transport, these have typically involved laboratory rodents and livestock, and little is known of its effect on non-human primates. This paper reports the results of a study of behavioural changes in a group of long-tailed macaques transported by air from standard breeding conditions and then re-housed in standard laboratory primate conditions. The animals were studied prior to their departure, immediately after their arrival, and 3 weeks after that. Data were collected on individual time budgets using focal animal sampling and on hierarchy using a feeding trial. The data were analysed for changes in behavioural repertoires and for social perturbation that would be reflected in hierarchical changes. Changes in behaviour occurred which reflected heightened levels of stress in the study group. It was also clear that although there was some adjustment of behaviour, after an initial change on arrival at the new establishment, there was no return to levels observed at the breeding facility within the first month. This study demonstrates that, as a whole, the process of international air transport and re-housing in laboratory conditions may result in the compromising of the welfare of the study animals.