The normal developmental expression of the Drosophila salivary gland secretion protein gene Sgs-3 requires the interaction of a distal and proximal regulatory element. A deletion/replacement analysis of the proximal promoter in stably transformed lines shows that induction of an Sgs-3/Adh fusion gene is normal if sequences from +10 to -50 are replaced by those of the hsp70 gene. Sequences between -98 and -50 are necessary for this expression but there is internal redundancy within this region as two distinct upstream sequences of 18 and 22 bp respectively are sufficient for stage- and tissue-specific expression, albeit at reduced levels. A point mutation at -53 eliminates the ecdysone-mediated repression of the Sgs-3 promoter at pupariation. We report mosaicisms of expression within the salivary gland for a number of stably transformed lines.