The Vibrio fischeri quorum-sensing signal N-3-oxohexanoyl-L-homoserine lactone (30C6-HSL) activates expression of the seven-gene luminescence operon. We used microarrays to unveil 18 additional 30C6-HSL-controlled genes, 3 of which had been identified by other means previously. We show most of these genes are regulated by the 30C6-HSL-responsive transcriptional regulator LuxR directly. This demonstrates that V. fischeri quorum sensing regulates a substantial number of genes other than those involved in light production.