This paper evaluates lidocaine absorption via oral mucosa following its topical application for symptomatic treatment of bone marrow transplantation (BMT)-induced oral mucositis. Five patients with high-grade oral mucositis after allogeneic BMT were entered consecutively into the study. Five healthy individuals served as controls. All 10 participants rinsed their mouth with 5 ml of a 2% lidocaine solution for 1 min, after which they expectorated the liquid. Blood samples were drawn at 1, 5, 10, 20, 30 and 60 min after rinsing and centrifuged. Plasma lidocaine levels were measured by fluorescence polarization immunoassay. In the BMT patients, plasma lidocaine levels were lower than the therapeutic range of this drug(0.2 µg/ml vs 1.5-5.5 µg/ml), while in the controls no detectable lidocaine levels were noted. The data from this preliminary study indicate that lidocaine prescribed as an anesthetic mouthwash in BMT patients with oral mucositis results in minor systemic absorption of the drug.