The triple combination chemotherapy of irinotecan, 5-fluorouracil and leucovorin (CPT-11/5-FU/LV or Saltz regimen) is the treatment of choice for patients with advanced colorectal cancer. Severe diarrhea, unfortunately, is a side effect of such treatment. Preclinical studies have indicated that the botanical drug PHY906 can reduce such diarrhea without compromising the effectiveness of the chemotherapy. The primary purpose of this clinical study is to evaluate the safety, tolerability and minimum effective dose of PHY906 when administered in conjunction with the Saltz regimen.