The purpose of this study was to describe the incidence, onset, duration, severity, and other relevant characteristics of mucositis and pain in patients undergoing bone marrow transplant (BMT) who were receiving high-dose chemotherapy (cytoxan, busulfan, and etoposide) without total body irradiation. A descriptive, longitudinal design was used to study a sequential sample of 47 patients undergoing allogeneic and autologous BMT. Each day, from 9 days prior to BMT through 21 days after BMT, nine anatomic regions of patients' mouths were assessed for extent and severity of mucositis. Oral pain was measured using the Short-Form McGill Pain Questionnaire. Forty-two patients (89%) developed mucositis, which, on average, began 3 days after transplant, lasted 9.5 days, and resolved by 12.6 days post-transplant. Thirty-six patients (86%) reported pain that began, on average, 4.5 days after transplant, lasted 6.5 days, and resolved by 11 days post-transplant. During the initial weeks following BMT, systematic assessment of the oral cavity areas that are at high risk for mucositis should assist nurses in detecting early oral complications and in initiating specific interventions. Additionally, attention needs to be given to the assessment and management of mucositis-related oral pain. Future nursing research should be conducted to examine efficient clinical methods of assessing mucositis and oral pain and to test prophylactic and therapeutic interventions.