This study assessed and analyzed the early oral changes following chemoradiotherapy and bone marrow transplantation. The most notable changes involved mucosal color (white and red), atrophy, vascularity, ulceration, increased salivary viscosity and xerostomia, and the patients' subjective complaints of dryness and oral pain. The ventral tongue, buccal and labial mucosa, and marginal gingiva manifested the most notable changes, while the palate was least affected. The overall trend was for the oral changes to begin slightly before transplantation, to worsen over the first 2 weeks after transplantation, and then to resolve progressively over the remainder of the study period. These oral changes appear to result from a number of insults, including the conditioning chemoradiotherapy, posttransplant immunosuppressive chemotherapy, xerostomia, local trauma, oral infections (especially those caused by HSV), and possibly acute GVHD. Oral HSV infection and/or acute GVHD should especially be considered if the oral status markedly worsens 21 days or more after transplant.