The most recent European housing and care regulations for laboratory rats mandate provision of a structured environment and group housing. Dividing structures and shelters in the cage offer rats opportunities to seek or avoid contact with other group members and hence are regarded as beneficial to animal welfare. In order to compare the physical environment of the IVC and the open cage, temperature, relative humidity, lighting and sound levels of the cages were measured. BN/RijHsd and F344/NHsd male rats were used, and they were housed in IVC- or open cages of the same type, three rats per cage, one of them carrying a telemetric transponder. Four groups and a crossover design were used: two groups with a maze made of crossing two aspen boards, a rectangular aspen tube group and controls. In one maze, drilled holes were loaded snugly with food pellets; rats had to gnaw wood to gain access to their food. Rats and food were weighed before and after each study period. The means of locomotor activity and means and coefficient of variations for mean arterial pressure (MAP) and heart rate (HR) were calculated for days 2, 6, 10 and 14 in each period. As a way of determining which of the statistically significant MAP and HR mean changes were biologically meaningful, the corresponding night-day differences of the controls were used in this two step assessment. On day 8 of each two week period, the rats were changed to clean cages and on day 11 exposed to IG-gavage. The means of activity, mean arterial pressure and heart rate were processed for the first hour subsequent to the procedure and thereafter separately in the light and dark periods and for the two cage types. Baseline values for each rat, for both dark and light and cage types were calculated from recordings made 24 h earlier; and these were subtracted from the corresponding response values. In the study of the physical environment of the cage types, there were differences in all measured parameters. In F344 rats, diet board was more effective in controlling weight, but when combining the strains, all comparisons with diet board were significant. In both cages, the F344 rats were generally more active than the BN rats during the dark phase, but not during the light phase. In the IVCs, both board types lowered MAP of F344 rats throughout the two week period and at the end of that period. Plain board was found to be the better of the two; hence dividing walls with or without restricted feeding seem beneficial for the welfare of F344 rats. None of the MAP or HR differences in BN rats were biologically significant. The MAP CV results showed that cage furniture may be used to achieve a considerable reduction value in blood pressure studies, but the outcome is strain-specific. Neither of the strains exhibited any statistically significant differences in faecal corticosterone or IgA excretion to these items. Based on the MAP results, the tube appeared to be a poor choice for F344 rats, whereas for BN rats, all furniture items seemed beneficial, with both board types apparently superior to the tube. In general, F344 rats had higher faecal corticosterone levels than BN rats with the reverse being true for secretory IgA values. In conclusion, LA and cardiovascular parameters seemed appropriate ways to evaluate the impact of cage furniture on physiological parameters, and covered structures such as tubes do not seem to provide any refinement value in these two rat strains.