A motile, chemotactic, Ogawa strain of Vibrio cholerae was attracted by all 20 L-amino acids tested, in contrast to Escherichia coli AW 405, which did not react to several of these. The maximum number of vibrios entering a capillary was much lower when the capillary contained carbohydrates rather than amino acids, but the minimum effective concentrations of the carbohydrates and amino acids tested were of the same order of magnitude. L-Fucose, a sugar known to inhibit the adhesion of this vibrio strain to brush border membranes, had no attraction (taxin activity) for it. A pepsin digest of rabbit mucosal scrapings or tryptone attracted vibrios as strongly as the most active amino acids. Several nonchemotactic and one nonmotile mutant were selected from the parent vibrio. The nonchemotactic mutants were indistinguishable from the parent in their ability to attach in vitro to isolated intestinal brush border membranes, whereas the nonmotile mutant had lost this ability. Parent and nonchemotactic mutants had equal growth rates in stirred and still continuous flow cultures that were maintained in an anaerobic environment.