Genetically similar mutants of Schizosaccharomyces pombe that failed to grow but survived at 44 degrees C for 72 h, exhibited a significantly delayed thermal death. These thermotolerant mutants registered a decrease in ethanol production by 25-50% at low as well as high temperatures. The data on tetrad products derived from crosses of mutants with the wild type parent, corroborated the constant co-segregation of thermotolerance and low ethanol production and most probably under the influence of a single gene, tet1. Reduced ethanol tolerance of mutant strains seemed to have been a probable reason for low ethanol production.