Preliminary results of the investigations conducted in a deep-litter barn were presented in the paper. The research was carried out during the summer season, from June till August 2014. Results of continuous measurements of the indoor temperature and air humidity revealed considerable diversification of the temperature and humidity conditions in the barn. Exceeded limit indoor temperature was registered, particularly in July when the ambient temperatures were high. The most unfavourable indoor conditions in the building occurred in July during 24 days of animal rearing. In the other analysed months (June and August) the recommended value of the indoor air temperature was noted during 13 days of animal rearing. The indoor air relative humidity also exceeded the maximum permissible values, although the animals remained on the pasture for a major part of the day. ...