Bile peptone broth and alkaline peptone water (pH 8.5) were examined as enrichment media for the isolation of Plesiomonas shigelloides from stools, with salmonella-shigella agar as the isolation medium. After 423 parallel examinations in two different experiments, bile peptone broth enrichment for 24 h was observed to be six times more effective (P less than 0.01) than direct plating alone on salmonella-shigella agar. Bile peptone broth was found to be twice as effective as alkaline peptone water for the recovery of P. shigelloides from stools.