The dynamics of transcripts of anti-apoptotic BI-1 gene in wheat plants (Triticium aestivum L.) of cv. Moscovskaya 39 subjected to low (4 and –2 °С) and high (37 and 43 °С) hardening and damaging temperatures was studied. It was shown that cold tolerance in plants was raised under the impact of low hardening temperature (4 °C), accompanied in the initial stage by the accumulation of transcripts of BI-1 gene. In contrast, cold tolerance and BI-1 mRNA level decreased under the impact of low damaging temperature (–2 °С). The impact of high hardening temperature resulted in an increase of thermal stability of plants until the end of the experiment (the 3 rd day). The content of BI-1 transcripts rose significantly under the same conditions in the initial period of exposure and then remained unchanged. The influence of high damaging temperature (43 °C) led to a rapid increase in plant thermotolerance and the expression level of BI-1 gene in the initial period of exposure, followed by a sharp decline of these indicators. The data obtained suggest that thermotolerance in plants can vary not only quantitatively and qualitatively, but the expression of anti-apoptotic BI-1 gene changes differently as well, depending on the nature (low or high) and intensity (hardening or damaging) of temperatures.