3695 Background: In wealthy societies, most patients with colorectal cancer are treated with curative intent and enter some type of follow-up regimen but the optimum surveillance strategy has not been defined. There are no active adequately-powered trials dealing with this topic originating in North America, as far as we are aware, but one is open in Europe (Gruppo Italiano di Lavoro per la Diagnosi Anticipata - GILDA). Methods: After primary curative-intent treatment, stratification, and randomization at GILDA headquarters, colon cancer patients are followed according to a more intensive or less intensive surveillance regimen. Rectal cancer patients are also followed according to a more intensive or less intensive regimen; these arms are similar to the arms for colon cancer patients but focus more on local-regional recurrence. To ensure adequate statistical power, the target number of patients is 1,500. Health-related quality of life and cost-effectiveness measures are incorporated in the trial. Results: The trial opened in 1998; 1,089 patients from 42 centers had been enrolled as of October, 2004. There were 537 and 552 patients in the more and less intensive trial arms, respectively. The trial opened to North American centers in 2002. The mean duration of follow-up was 21 months as of October, 2004. Seventy-nine relapses, 37 deaths, and 9 second primary cancers had been documented in the two more intensive follow-up arms; 72 relapses, 27 deaths, and 11 second primary cancers had been observed in the two less intensive arms as of October, 2004. Conclusions: This trial should provide the first evidence based on an adequately powered randomized trial to determine the optimal follow-up strategy for colorectal cancer patients. The authors will provide information packets at the meeting for individuals and institutions interested in participating in this trial. No significant financial relationships to disclose.