The tet-regulatable promoter system is commonly used for genetic studies in many eukaryotic organisms. The promoter is regulated using doxycycline. There are no obvious phenotypic effects observed when doxycycline is added to the growth medium of yeast to control expression from the promoter. It is widely accepted that doxycycline is innocuous to yeast. Global genetic studies are now commonplace and the tetO-system is being used in transcriptome studies. Hence, we wanted to ensure that the absence of phenotypic effects, on addition of doxycycline to the growth medium, is mirrored in transcriptome data. We have demonstrated that doxycycline has no significant effect on global transcription levels and will continue to use the tetO-regulatable promoter system for genetic studies.