The efficiency and safety of charcoal nanoparticle tattooing in localizing unpalpable colonic small lesions for later laparoscopy is described. Twenty six patients were enrolled for this prospective study. Tumor sites were localized with charcoal nanoparticles during colonoscopy for later laparoscopic colorectal operations. In all patients, the entire colon was examined preoperatively by colonoscopy and 0.5 ml (5 mg) of charcoal nanoparticle was injected submucosally near lesions or polypectomy sites. During laparoscopic colorectal operations for these biopsy-proven tumors, tumors were easily identified. The mean resection margin was 3.13 +/- 2.01 cm. The mean length of resected intestinal segment was 12.69 +/- 4.39 cm. No tumor was found at the resection line as indicated by postoperative pathological examination. Most importantly, no wrong segment was resected. Thus we show that easy identification of tumor can be achieved by preoperative tattooing with charcoal nanoparticles. Further studies regarding the long-term tattooing of tumor with charcoal nanoparticles are warranted.