Background. In cases of synchronous colorectal hepatic metastases the primary colorectal cancer maintains a strong influence on the metastases, so the possibility of occult hepatic and extrahepatic metastases must be kept in mind. Our treatment policy has been to reevaluate the metastases at an interval of 3 months after colorectal resection and determine treatment strategy. We examined the appropriateness of interval hepatic resection for synchronous hepatic metastasis.Methods. Study1. The subjects were 164 patients who underwent resection of hepatic metastasis of colorectal cancer (synchronous, 70 patients; metachronous, 94 patients) between January 1983 and December 2003. Background factors for hepatic metastasis and postoperative results were compared for synchronous and metachronous cases. Study2. Of the patients who underwent colon resection at our hospital between 1995 and 2005, the treatment course was investigated for 28 interval patients with no extrahepatic lesion remnants at colorectal surgery and a simultaneously resectable liver(H1 group). Results. Study1. The cumulative survival rate for 164 patients at 3, 5, and 10 years postoperatively was 71.9%, 51.8%, and 36.6%, and the post-resection recurrence rate in remnant livers was 26.8%. Interval resection for synchronous hepatic metastases was conducted in 49 cases after a mean interval of 131 days. No difference was seen in postoperative outcome between synchronous and metachronous cases. Study2. The treatment course in the H1 group was decided after an observation interval. Hepatic resection was not indicated in 9 of the 28 patients during the interval. New lesions appeared during the interval in 7 of 19 interval hepatic resection patients. In 16 of 28 (57%) interval patients there was a change in the hepatic resection procedure or surgical indications.Conclusion. Delaying resection allows accurate understanding of the number and location of hepatic metastases, and is beneficial in determining candidates for surgery and in selecting surgical procedure.