This study aimed to investigate the sugar beet genotypes for resistance to hyperthermia and obtain temperature-resistant lines. Nine hybrids and one variety of sugar beet were screened. Cotyledonary leaves and hypocotyls isolated from aseptic seedlings were used for induction of callus and subsequent subcultivation. To create hyperthermic conditions, the callus lines were maintained in thermostats at temperatures of +27°C, +41°C, +45°C, and +47°C. The effect of high temperatures on the callus tissue was assessed by the specific callus diameter index. The free proline was detected with chromatography. As result of callus tissue exposed to temperatures of +41°C, 45°C and 47°C, on the 9th day of cultivation at high temperatures, significant differences were observed in the size and colouration of the callus tissues. At a moderate temperature (+41°C), the growth of the callus mass was somewhat higher compared to the control. At a high temperature (+45°C), the intensity of the growth processes decreased and ceased at a temperature of +47°C. After transfer and subsequent cultivation of callus tissues in regeneration medium MSR Murashige and Skoog medium for regeneration, all genotypes demonstrated the formation of morphological structures that initiated the formation of regenerated plants. The number of regenerated plants largely fluctuated over temperatures and almost was not related to genotypes. Consequently, the temperature-resistant lines obtained as a result of extreme heat treatment, differ in terms of the specific diameter of callus.