Gram stains of stools from patients with diarrhea and control patients with no diarrhea were examined for a predominance of gram-positive rods and the presence of polymorphonuclear leukocytes. Results were compared with those from lower gastrointestinal endoscopy for pseudomembranes. Clostridium difficile culturing, and C. difficile toxin assay. The Gram stain was moderately difficult to interpret and was not useful in diagnosing diarrheal disease associated with C. difficile.