We investigated the effectiveness of prophylactic FOLFOX after curative resection of synchronous metastases in patients with colorectal cancer (CRC). Clinicopathological information including postoperative chemotherapy, such as a therapeutic regimen, relapse-free survival (RFS), site of recurrence, etc., was retrospectively analyzed in 116 CRC patients with synchronous distant metastases, and 63 patients with metachronous metastases who had received surgery in our hospital between 2000 and 2009. Fifty-three patients (84%) out of 63 without adjuvant chemotherapy, and 38 (83%) out of 46 patients that received oral or intravenous 5-fluorouracil (5-FU) (alone or with leucovorin (LV)or isovorin) developed recurrent tumor(s) afterwards. The median RFSs were 119 and 281 days, respectively. By contrast, a single patient among 6 who underwent FOLFOX (up to 12 therapeutic courses) showed recurrence 476 days after surgery. The RFS of the FOLFOX was significantly higher than that of the 5-FU (+LV) or surgery alone (p=0. 03, p=0. 007, respectively). In conclusion, the FOLFOX regimen is more beneficial for CRC patients with synchronous metastasis as adjuvant chemotherapy than 5-FU (+LV) or other followup strategies.