The aim of this study was to assess prospectively the efficacy of granulocyte-macrophage colony-stimulating factor (GM-CSF) in the management of chemotherapy-induced oral mucositis in nonneutropenic cancer patients. In a prospective open study, 30 cancer patients with chemotherapy-induced, neutropenia-independent oral mucositis were treated with GM-CSF (Schering Plough Corp, Kenilworth, NJ) prepared as a mouthwash solution (5-10 mu g ml(-1)). GM-CSF was administered within 24 hours of occurrence of oral mucositis x 4 to 6 times daily. Systemic GM-CSF was not permissible. Oral mucositis was graded according to the modified Radiation Therapy Oncology Group criteria. Six patients were subsequently excluded as they experienced neutropenia during GM-CSF therapy. The remaining 24 patients were all evaluable. Most patients had either Grade 3 or 4 gross (76%) or functional (54%) mucositis. The mean +/- SEM gross oral mucositis scores for all 24 patients combined decreased from 3.08 +/- 0.18 at baseline to 2.04 +/- 0.19 (p < 0.0001) after 2 days, 0.92 +/- 0.16 (p < 0.0001) after 5 days, and 0.25 +/- 0.09 (p ( 0.0001) after 10 days of therapy. Likewise, the mean +/- SEM functional oral mucositis scores decreased from 2.71 +/- 0.18 at baseline to 1.58 +/- 0.19 (p < 0.0001) after 2 days, 0.75 +/- 0.16 (p < 0.0001) after 5 days, and 0.17 +/- 0.08 (p < 0.0001) after 10 days of therapy. The duration of severe oral mucositis was also shortened as Grade 0 or 1 (gross mucositis score) was evident in seven (29%), 20 (83%), and 24 (100%) patients by the 2nd, 5th, and 10th day of therapy, respectively. Similarly, Grade 0 or 1 (functional mucositis score) reported in 13 (54%), 19 (79%), and 24 (100%) by the 2nd, 5th, and 10th day of therapy respectively. It was found that GM-CSF mouthwash as used in this study has a significant recuperative efficacy on the severity, morbidity, and duration of chemotherapy-induced oral mucositis. A large randomized, placebo-controlled study is warranted to ascertain that benefit and determine the optimal dosages and schedule.