Background and Aims: Imipramine, a tricyclic antidepressant and a non-specific inhibitor of Eagl potassium channel, is used for the management of depression and cancer pain, and was shown to reduce the cell viability of HT-29 cells.Imipramine administration was also proved to reverse the tumoral growth facilitated by chronic variable stress.The present study was designed to evaluate the effect of cell growth, cell cycle and apoptosis of imipramine against colon cancer using HT-29 cells, and to elucidate the molecular mechanisms.Methods: Human colon cancer HT-29 cells were grown with routine cell cultivation and cells were treated with different concentration of imiprmine.Cell survival was determined by the MTT assay, cell cycle distribution was assessed by FACS flow cytometer analysis after stained with propidium iodide, apoptosis of HT-29 cells was detected by Annexin V/PI methods and DNA ladder assay.Expression level of Eagl protein was detected by Western blot, and mRNA of p21, p27, cyclin E 1 and CDK2 was inspected by reverse transcription-polymerase chain reaction.Results: Cell viability decreased dose-dependently and time-dependently after treatment with imiprmince in HT 29 cells.Cell cycle arrested during the G0/Glphase accompanied by the induction of apoptosis in a dose-dependent manner.Results of a DNA ladder assay revealed that DNA ladders appeared with imipramine treatment in HT-29 cells at dosage of>50 μM.Expression level of Eag1 protein was decreased in a dose-dependent manner.p21 mRNA and p27 mRNA were upregulated, and CDK2 mRNA and cycline E1 mRNA were suppressed in imipramine-treated HT-29 cells in a dose-dependent manner.Conclusions: Imipramine, a non-specific inhibitor of Eag1 potassium channel, induced cell growth inhibition, cellcycle arrest and apoptosis in HT-29 cells through upregulation of p27 and/or p21.