The nucleotide sequence of the Vibrio alginolyticus scr repressor-encoding gene (scrR) was determined. The deduced amino acid sequence of the scr repressor was homologous with the gal, lac and cyt repressors of Escherichia coli and contained a helix-turn-helix DNA binding domain. Although the scrR gene encoded a protein which was required for the regulation of the V. alginolyticus sucrose utilization system, a particular deletion in the scrR gene could not be complemented in trans. The lack of complementation was discussed in terms of the possible involvement of a cis regulatory element or interference by the truncated scr repressor.