We present a 72-year-old male who developed progressive, watery diarrhea despite anti-motility agents. On colonoscopy, the mucosa was inflamed and covered with an exudate. Stool studies for Clostridium difficile and Escherichia coli were negative. Biopsies revealed pseudomembranous collagenous colitis, a rare form of microscopic colitis. His symptoms improved dramatically with budesonide therapy.