A trial was conducted to compare the effectiveness of povidone iodine and chlorhexidine digluconate with buffered peroxyborate in the treatment of acute ulcerative gingivitis. After 20 patients had entered the trial and 11 had required additional therapy with metronidazole to control their symptoms, the study was terminated. Those patients receiving peroxyborate all showed a satisfactory improvement in clinical signs and symptoms. One patient each receiving povidone iodine or chlorhexidine reported a symptomatic improvement, although gingival ulceration was still apparent at 1 week. The remaining patients all required metronidazole therapy to control their symptoms. Povidone iodine and chlorhexidine digluconate therefore cannot be recommended for the treatment of acute ulcerative gingivitis.