This study aimed to assess the time needed by rats, which had not been previously transported, to acclimatize to a new environment after 5 h of van transport, using physiological parameters as measures of acclimatization. Animal shipping boxes and transport van conditions were standardized to minimize stress factors that could be associated with transport. Heart rate (HR), body temperature and activity levels were measured in the rats before and after transport using previously implanted radiotelemetry transmitters. Body weight was also recorded. All parameters were changed significantly except for body temperature. Results suggest that rats take three days to acclimatize to a new environment, as measured by the physiological parameters of body weight, HR and activity. © Laboratory Animals Ltd.