We have used P-mediated transformation to introduce into the Drosophila genome transposons containing the hsp-70 heat shock promoter (hsp) placed at different distances upstream of the white gene. Using these constructions we found a strong terminator 250 nucleotides upstream of the white transcription start. When all white upstream sequences are deleted and the hsp is fused to the white leader region, white transcription is under hsp control, however, flies carrying this construction have red eyes even at low temperature, due to the basal level of activity of the hsp. High levels of transcription are obtained after heat shock but about half of the transcripts are incompletely spliced. One transformed line carries the transposon integrated near the heterochromatin. These flies have very pale eyes but develop strongly pigmented, variegated eyes if heat shocked in the first 2 days of the pupal stage. Heat shocks after eclosion have no effect on eye pigmentation. The properties of these transposons also indicated that the control sequences required for Zeste interaction lie > 1 kb upstream of the white transcription start while those required for dosage compensation are close to the gene.