Abstract. The complex pattern of action for cell viability makes the heat shock protein (HSP) loci to potential candidate genes for stress susceptibility. In the bovine hsp70.1 gene a functional AP2 box variant affecting a significant decrease of cellular stress response, was described. To monitor the distribution of this promoter variant in phenotypically different populations a diagnostic PCR-RFLP assay was developed. As an indicator for individual stress susceptibility the phenotypic trait "productive life" was measured based on the assumption that animals having longer "productive life" might be superior in coping with stress during lifetime. Association of the observed promoter variant with the estimated breeding value "productive life time" was studied in a Holstein sire population and a granddaughter design. Our observations suggest that this polymorphism affects productive life in cattle. Animals with a normal AP2 box are characterised by an increased stress tolerance concluded from their prolonged productive life. These results are supported by the observed different distribution of the hsp70.1 promoter variant in cows of different lactation numbers and degree of selection. Frequency of the mutant hsp70.1-AP2 box allele is significantly lower in cows selected as dams of sires and in cows with an increased lactation number. Additionally, cows with a mutant hsp70.1-AP2 box variant exhibited an increased hazard for culling.