We have constructed a gene fusion using the promoter of Drosophila hsp70 and the structural gene for Drosophila alcohol dehydrogenase (Adh) and used this construct to transform Adh-deficient flies. In these transformants, Adh is expressed only after heat shock. Like hsp70 itself, this heat-shock-inducible Adh (Adhhs) is induced in a wide variety of tissues. It fails to be induced in primary spermatocytes. Although the tissue distribution of Adh activity is very different from wild type, this does not appear to be deleterious. Indeed, the induction of Adhhs allows flies to survive exposure to ethanol. We have used this latter characteristic to select dominant, trans-acting mutations that alter the response of flies to heat shock.