The underlying mechanism of high-dose therapy (HDT)-related oral mucositis (OM) may be partly mediated by alterations in the normal salivary composition. This study evaluated salivary antioxidant and immunological capacities observed in myeloma patients suffering from HDT-related OM, and assessed potential contribution of these factors to OM development. Twenty-five consecutive myeloma patients treated with melphalan 200 mg/m(2) followed by autologous SCT were enrolled. Patients underwent a daily assessment for OM, and salivary samples were collected on days -3 and +7 of transplantation and analyzed for secretory IgA and antioxidant capacity. The degree of mucosal damage was assessed by measuring the salivary carbonyl and albumin (Alb) levels. OM, reported in 96% of patients, appeared to be most severe on 8 day after transplantation (range: +2 to +14). Clinical mucositis was associated with significant reduction in salivary secretory IgA (54%; P=0.05), and antioxidant activity, measured by total antioxidant status (40%; P=0.0004), antioxidant capacity (ImAnOx) (23%; P=0.002) and uric acid level (51%; P=0.006). The increase found in salivary Alb (119%; P=0.024) and carbonyl (28%; P=0.047) levels, indicates mucosal and oxidative damage, respectively. These salivary changes might enhance mucositis development and symptoms. Therapeutic interventions, enhancing antioxidative and immunological activities need to be investigated.