Mucosal toxicity is an incapacitating complication of intensive chemo-radiotherapy for children with malignant disorders, and is physically and psychologically distressful. It is therefore important to minimize mucosal toxicity in those patients. In this report, the effects of the combined prophylaxis of oral cooling (cryotherapy) and administration of propantheline, an anticholinergic drug, were studied in patients (aged 2-16 year) with acute leukemias or solid tumors, who underwent myeloablative chemo-radiotherapy and autologous peripheral blood stem cell rescue from 1993 to 1997. Patients were pretreated with the combined prophylaxis (n = 12) or single prophylaxis (n = 5), or left untreated (n = 7). The combined prophylaxis significantly reduced the severe mucositis (combined, 8.3%; single, 20.0%; and untreated, 42.9%) and severe diarrhea (combined, 16.7%; single, 60.0%; and untreated, 57.1%). Moreover, the combined prophylaxis tended to shorten the periods of febrile episodes defined as temperature > 38°C (combined, 3.8 days; single, 4.6 days; and untreated, 5.6 days). Therefore, the combination of propantheline and oral cryotherapy may be feasible and effective for reduction of mucosal toxicity in patients with malignancy who undergo high-dose chemotherapy.