Levobupivacaine (LEVO) is a new , long-acting amide local anesthetic . The physicochemical properties and anaesthesia potence of LEVO and Bupivacaine (BUPI) appear similar . The central nervous system toxicity and cardiotoxicity of LEVO is less than that of BUPI. LEVO can be used extensively in clinic . Nowadays, the pharmacodynamics of LEVO have been widely clinically studied in China, but no pharmacokinetic properties have been reported . This study is to investigate the pharmacodynamics and pharmacokinetics of LEVO for lumbar epidural anesthesia in , and provide theoretical bases for rational administration of LEVO during clinical anesthesia. 1.Material and Method1.1  Material   This study included 20 patients (ASA Ⅰ ~ Ⅱ , aged 32~59 years) . They were scheduled to undergo elective colon or rectum tumor surgery under epidural     combined     general     anesthesia.     They     were     randomized     into Group Ⅰ (0.75%LEVO , n=10) and Group Ⅱ (0.5%LEVO , n=10) . Epidural block was performed at the L_(1.2) interspace . Patients of Group I  and II received 0.75% and 0.5%  LEVO  2 mg·kg~(-1)  with  adrenaline  2.5 μg·ml~(-1)  epidurally in  1.5  min  , respectively  .  After  30  min  ,  general  anesthesia  was  induced  with  sodium hydroxybutyrate (60~80 mg·kg~(-1)) ,  remifentanil (2 μg·kg~(-1)) and scoline (1.5 mg·kg~(-1))  . The trachea was intubated and anesthesia was maintained with inhalation of nitrous oxide and oxygen (1:1) , intravenous infusion of remifentanil and intermittent intravenous boluses of atracurium when needed .1.2 Determination of pharmacodynamics