The effect ofN-1-(3,5-dimethyladamantyl)maleimide (DMAMI) on the growth of Colo205 human colon cancer cells was examined bothin vitroandin vivo. Flow cytometry analysis showed a decrease of G2/M Colo205 cells at 4–6 h after treatment with DMAMI prior to accumulation of apoptotic cells at 24 h. Significant changes in cell morphology, i.e. shrinkage and chromatin condensation of cells, were observed after treatment with DMAMI. In the analysis of the apoptosis markers, it was found that the increase of Annexin V binding to membrane, peroxide radicals, dissipation of the mitochondrial membrane potential, and the activation of caspase-3, -8 and -9 were all evident at 4–6 h after treatment with DMAMI.In vivoanalysis showed that treatment of Colo205 tumor-bearing SCID mice with DMAMI (230 mg/kg, intratumoral, once) resulted in rapid tumor damage that leads to significant tumor growth inhibition and no obvious acute toxicity. These results suggest that DMAMI has potential for local treatment of cancer.