We have sequenced the yeast HSP90 gene, which encodes the (apparent) Mr = 90,000 heat shock-inducible protein of this organism. All sequences required for the heat shock-regulated expression of this gene reside on a segment of DNA containing no more than 273 nucleotides 5' to the transcription origin. Transcript mapping reveals that the mature hsp90 mRNA contains a 59-nucleotide 5' untranslated segment, a coding segment of 2130 nucleotides (sufficient to encode a protein of Mr = 81,419), and a 3' untranslated segment of 128 nucleotides. Although the sequences surrounding the coding region of the HSP90 gene are quite similar to those surrounding other sequenced yeast genes, we find as well a limited homology between sequences located 5' to this gene and the putative heat shock-regulatory sequences located 5' to the heat shock-inducible genes of Drosophila.