The objective of the present study was to investigate the influence of housing air temperature on the behavioural acts, physiological parameters and performance responses of fattening pigs. Animals were randomly allocated to 3 groups with 30 heads in each. During eight weeks of fattening, the animals of the two experimental groups were subjected to long-term technological temperature stress, provoked by a significant deviation of the microclimate parameters. The first control group of animals was kept following the Departmental Norms for Technological Design - Agro-Industrial Complex - 02.05 «Pig-breeding enterprises (complexes, farms, small farms)» at an air temperature of +17…+21 °C; pigs of the second experimental group were kept at a temperature of - +5…+8 °C, and the third experimental group - +28…+31 °C. During the experiment, the timing of behavioural acts and their index assessment, physiological parameters and productive characteristics of fattening pigs were studied. The experiment results showed that the thermoneutral zone for fattening pigs is + 17… + 21 °C. Animals 2nd experimental group showed less movement (P < 0.001), used huddling for decreasing body heat loss, more feed intake (P < 0.01), which increased its conversion, had reduced HR, RR, RT. Pigs of the 3rd experimental group showed increased movement (P < 0.001). This can be explained by their desire to find a cool place and rest lying on the side, consuming more water, having high HR, RR, and RT, showing signs of hyperthermia and were characterized by low-performance responses.