In this study, observations on traditional methods, such as open field test, conicosterone assays and monitoring of barbiturate sleeping time, were performed to validate the impact of housing conditions on the welfare of rats and mice in orderto compare the outcome with observations previously achieved by preference tests and telemetry. These traditional methods failed to demonstrate the impact on the animals caused by grid housing previously shown by telemetry and preference studies, and it is, therefore, concluded that these traditional tests may be less sensitive for monitoring Subtle small environmental impacts on laboratory rodents.Although. the methods were not able to reveal any differences in eortieosterone level and open field test between housing conditions, there were significant differences between mouse strains and sexes. These differences between strains should betaken i nto account when choosing the best suitable strain for a study
