Decreased growth is often used as a phenotypic measure in gene perturbation experiments in model systems such as yeast. O'Duibhir et al. have now shown that various mutant yeast strains exhibit slow growth that is characterized by a specific gene signature. This signature was highly similar to the known gene signature of environmental stress response, even though the mutant strains were grown under ideal conditions. Subtraction of this slow growth signature from future experiments involving environmental perturbation may therefore yield gene signatures that are more specific to the perturbation and that are not simply a reflection of slow growth.