Production of two pigmented antibiotics, actinorhodin and undecylprodigiosin, is differentially affected in Streptomyces coelicolor A3(2) at high salt concentration, with actinorhodin being inhibited and undecylprodigiosin activated. Analysis of expression of two genes coding for pathway-specific transcriptional regulators of actinorhodin and undecylprodigiosin synthesis, actII-ORF4 and redD, revealed that their expression is similarly differentially affected. Thus, the effect of high salt concentration on actinorhodin and undecylprodigiosin production is mediated at the transcriptional level by the differential expression of genes encoding corresponding pathway-specific transcriptional regulators.