Colorectal cancer will be diagnosed in approximately 150,000 patients in the USA this year. Chemotherapy has recently been shown to improve survival when given as adjuvant therapy to surgery in patients with stage III colorectal cancer. Demonstration of this benefit required large, randomized controlled trials. Either 5-fluorouracil (5-FU) and leucovorin for 6 months or 5-FU and levamisole for 12 months are currently considered standard adjuvant treatment for stage III colorectal cancer. However, current adjuvant trials are comparing continuous infusion and intravenous bolus 5-FU regimens and oral uracil/Ftorafur with intravenous 5-FU and leucovorin, as well as studying the timing of chemotherapy in the adjuvant setting. Subsequent adjuvant trials will examine newer regimens with activity in advanced colorectal cancer, as well as the efficacy of monoclonal antibodies. Other trials will study which type of surgery is optimal and whether adjuvant therapy is helpful in stage II colon cancer. Trials in metastatic disease will focus on combinations of newer agents which may improve survival in this patient group. Studies in rectal cancer will focus on determining which agents are optimal in combination with radiation therapy in the adjuvant setting. Molecular characteristics of tumor cells are being defined, which may guide therapy in the future. Careful, logically designed clinical trials will hopefully provide more efficacious therapy for this common cancer.