Abstract: A sensitive and highly specific TLC method for determining serum level of carbamazepine is presented. Serum (1μ1) was spotted directly onto the thin-layer plate, separated spots werè converted into compounds with fluorescence by exposing the plates to hydrogen chloride gas for 10 min and immediatly heating the plates for 10 min at about 160℃. The fluorescence was measured quantitatively using a CS-920 TLC scanner equipped with a fluorescence attachment.The relation between peak area and concentration of carbamazepine in serum was linear from 4～16μg/ml. The lowest concentration of detection was about 2μg/ml. The CV was 3.25～10.0%. The recovery of carbamazepine in serum was about 99%. The result was not interfered by some commonly administered drug. The method well meet the needs of therapeutic drug level monitoring.