A clinical trial involving 462 colon, rectum, and breast cancer patients randomized among four different dosage regimens of 5-FU (an intravenous loading course, a weekly intravenous schedule, a nontoxic schedule, and an oral schedule) has shown a significantly better response among colon-rectum cancer patients for the intravenous loading course. In addition, duration of response and time to progression are also significantly better. Overall survival is approaching significance for the colon rectum group (p value .082). In contrast, breast cancer patients show little difference between treatments. Toxicity is somewhat higher for the loading course.