Objective : The purpose of this study was to compare the plasma amitriptyline and nortriptyline level between before and after fluoxetine addition with patients who were currently taking amitriptyline. Method : From the inpatient and outpatient unit of Soon Chun Hyang University Hospital, Chunan, fourteen subjects who were taking amitriptyline 25mg more than 1 week at least were given fluoxetine 20mg. Before and 2 weeks after fluoxetine addition, the plasma level of amitriptyline and nortriptyline are analyzed simultaneously by High Performance Liquid Chromatography(HPLC). At the same times, HAM-D(Hamilton Rating Scale for Depression) score and the UKU(Uldvalg for Klinske Unders${Phi}$ gelser) side effect scale were checked. Results : After fluoxetine addition to the patients who were taking amitriptyline, the plasma level of amitriptyline, nortriptyline and sum of amitriptyline and nortriptyline had risen. The mean plasma amitriptyline level increased from $168.9{pm}89.4ng/ml$ to $183.0{pm}102.0ng/ml$ after fluoxetine addition(p=0.011), but the change was not statistically significant. The mean plasma nortriptyline level increased significantly from $114.3{pm}70.2ng/ml$ to $168.0{pm}86.2ng/ml$ after fluoxetine addition(p=0.011). In addition, the mean plasma level of total amitriptyline and nortriptyline increased significantly from $283.1{pm}125.3ng/ml$ to $350.9{pm}78.4ng/ml$ after fluoxetine addition(p=0.016). After fluoxetine addition, no significant change was noted in the UKU side effect scale score. Conclusion : As consequence of comparison of plasma amitriptyline and nortriptyline level before and after fluoxetine addition, mean amitriptyline, nortriptyline and total plasma level was increased after fluoxetine addition. This suggests that coadministration of amitriptyline and fluoxetine may induce improvement of depressive symptom in depressive patients by way of increased plasma level of amitriptyline.