Transpositional activity of mobile elements can be induced by different environmental stresses. Here, we present evidence that transposition of Tn4652 is elevated in stationary-phasePseudomonas putida and suppressed in an isogenic ς^S-defective strain. We demonstrate that transcription from the Tn4652 transposase promoter is controlled by the stationary-phase-specific sigma factor ς^S. To our knowledge, this is the first example of direct stationary-phase-specific regulation of a mobile element transposase. Data presented in this report support the idea that activation of transposition under stressful conditions could be an inducible process.