Introduction: The fattening cattle kept in the intensive feeding conditions is exposed to various stressful situations. The reasons are the technological breeding solutions combined with other fattening management methods. It has been noted that the animals react to such situations with health problems, lowered growth rate, as well as the change in behaviour and impaired well-being. An effective environment enrichment should decrease the frequency and/or the intensity of abnormal behaviour, and increase the scope of expressing the characteristic behaviour patterns, as well as help the animals to deal with stressors from the environment. Aim: The principal aim of this dissertation was to ascertain the influence of an enriched environment on the behaviour, welfare and production results of fattening cattle, with the enriching materials being the grooming brushes and salt licks. Material and methods: In view of the fact that the lack of space is one of the major reasons for abnormal social behavior, the effects of the enriching materials were tested with the fattening cattle kept at different stocking density. Both field and laboratory tests were conducted with this aim in mind. The field studies used the microclimate characteristics measurements in the facilities with fattening cattle, while the welfare assessment meant noting the frequency of aggressive and friendly modes of behaviour and stereotypy, the relationships between people and animals, the overall health and condition, as well as the frequency of using the enriching materials. Saliva samples were taken in order to ascertain the cortisol concentrations, indicating the levels of stress. At the laboratory, the saliva samples were treated by immunochemical methods. Results and conclusions: In using the enriching materials, a statistically significant difference (p<0.05) has been observed between the lower and higher density groups, while no significant difference has been observed in using the materials over the fattening months. It can be assumed that the higher stocking density of animals within the living facilities has resulted in frustration over the lack of space, prompting the higher use of the enriching materials, regardless of the fattening process phase, i.e. month. The fattening cattle used both the grooming brushes and the salt licks equally. The lower density group without the enriched environment had a significant (p<0.05) increase of head banging in comparison to all the other observed groups. Furthermore, it has been noted that the fattening cattle in the unenriched environment groups had a significantly higher (p<0.05) incidence of chasing among themselves in comparison to the enriched environment groups. The total of aggressive behaviour incidents was significantly higher (p<0.05) in both unenriched environment groups, which points to the conclusion that the enriched environment favourably influences the fatting cattle, holding their interest and meeting very specific needs. The frequency of friendly modes of behaviour was significantly (p<0.05) different between the higher stocking density groups and was significantly higher in higher density groups with enriched environment. The stereotypy had a much higher incidence rate (p<0,05) in the higher density and no enrichment group than in all other groups. That is why it can be concluded that the enriched environment had a positive effect on the development of friendly interactions between the individual animals and has decreased the frequency of stereotypy incidence. During the four months of fattening, the mean concentrations of cortisol in the animals' saliva, across the groups, ranged from 3.00 to 3.44 ng/mL. A statistically significant difference (p<0.05) has been determined in the differences in cortisol concentrations between the months of the fattening period, but not statistically significant between the groups themselves, while a statistically borderline interaction has been noted between the individual months of fattening period and the groups. It can be concluded that the enriched environment and the stocking density did not influence the cortisol concentrations in their saliva. The level of stress did not influence the growth, as evidenced by their final weight, almost identical in all the groups. Neither the enriched environment, nor the lower density have influenced the health status indicators, the fitness and growth of the fattening cattle. The stocking density and the enriched environment influenced the body cleanliness and the indicators of lying and chewing the cud. Significant correlation between the indicators of driving away other animals, making them move from its place and using the salt licks, of extremities alopecia and using the grooming brushes, and the indicator of lying down and chewing the cud with using the salt licks, confirm the assumption that the enriched environment has a positive effect on welfare indicators. The level of stress in fattening cattle has been assessed, for the first time in Croatia, using the saliva samples, as a less aggressive method than taking blood samples. In view of the lack of such studies in the world, focusing on the stress levels in fattening cattle, this research is a significant contribution to this field. The results suggest that the breeders should definitely enrich the fattening cattle environment, as it is one of the ways of improving their welfare and possibly surpassing the standard welfare levels.