We review recent developments in the diagnosis and treatment of colorectal cancer. In diagnosis, the detection of the APC gene mutation in stool samples has had a strong impact because of its practical usage for mass screening. Several reports have indicated that the molecular detection of a very small number of cancer cells in the peripheral blood, bone marrow, or lymph nodes yields adequate information on recurrent disease. Several new markers were reported as a significant indicators of cancer development, invasion, or metastasis. In treatment, determination of microsatellite instability may be useful to select good candidates for 5-fluorouracil-based chemotherapy. New molecular targets have been reported, including epidermal growth factor receptor inhibitor, matrix metalloproteinase inhibitors, etc. Gene therapy with p53 or FHIT had undergone successful clinical trials. Tumor-specific immunotherapy with dendritic cell vaccination has also been achieved. In conclusion, many efforts to overcome colorectal cancer will soon open new therapeutic windows.