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In this study groups of 4 female Han:Wistar-rats of three ages living in three different, non-enriched housing conditions, were compared. We used the cages Macrolon type III and IV as well as a plastic tub for guinea-pigs. The study was based on behaviour observations recorded by video tape, from which we developed ethograms. Following behaviour aspects were compared: - stay in nest - rest - maintenance behaviour - comfort behaviour - exploration - social behaviour and play - locomotion - bar-biting and behaviour anomalies After the video recordings the animals were tested in four different behaviour tests (Home Cage-Emergence-, Open-Field-, Box-Emergence-, Hole-in-the-Wall-Test). During the three-month investigation body weight, food and water consumption and the cage ammonia levels were registered as well Locomotor activity was monitored by two different detector systems. Postmortal the adrenal gland weights were measured. Results I) The animals in the guinea-pig-cage differ significantly from the other cage groups regarding their ethograms, their final body weight, their adrenal gland weight and their test behaviour. 2) The percentage of rest, maintenance-, comfort-, social- and play-behaviour within each age group is hardly influenced by the given cage size but by the containing structures. Maintenance and social activities decrease with higher age while exploration behaviour (especially upright exploration) increases. Adult rats are not able to perform the observational stance in cage type III. 3) Locomotion and intensive kinetic behaviour during play and exploration increase with a larger cage area. In cage type 111 running and chasing often is replaced by aggressive grooming. In contrast to the other cage types climbing on the cage lid is not possible. The measurement of locomotor activity confirms, that a much higher motion level is displayed in cage type IV. We were not able to find a suitable system to measure locomotor activity in the guinea-pig-cage. 4) Obvious behaviour deficiencies are rare, there is some bar-biting in type 111 and in the guinea-pig-cage as well as intention movements to climb in type 111, which can be evaluated as behavioural anomalies. 5) The results of above-mentioned behaviour tests show no evident differences between the cages type 111 and IV. 6) Regarding the development of body weight there is a tendency towards lower final body weights and higher adrenal gland weights with increasing cage size. These results differ significantly in the guinea-pig-cage. 7) Cage ammonia levels of adult rat groups in type III rise up to health-risky concentrations within three days. These levels are never reached in the larger housing conditions. We suggest to use the cage Macrolon type IV as a conventional housing system for laboratory rats, which is more suiting to the animals " demands than a cage type III.