An additional resection is indicated when colorectal polyps resected by colonoscopy reveal T1 carcinoma with unfavorable histology (no free margin or having risk factors for lymph node metastasis). We describe our experience with this type of surgery with the minilaparotomy approach (< or = 7 cm). This prospective study included 19 consecutive patients between 1997 and 2001. Specimens resected by colonoscopy revealed T1 carcinomas with one of the following histological types: inadequate excision (no free margin), lymph-vascular invasion, histologic grade III, or sm2/sm3 (submucosal invasion greater than 200-300 microm from the muscularis mucosa). The minilaparotomy approach included 15 colectomies and 4 anterior resections. Median length of minilaparotomy was 7 cm (range, 4-7 cm). Median number of lymph nodes removed was 11 (range, 7-21 lymph nodes). Median proximal and distal margins were 9.0 (range, 5.2-17.5 cm) and 8.5 cm (range, 2.0-11.5 cm), respectively. The patients quickly returned to normal function without morbidity and mortality. Five (26.3%) had a residual carcinoma within the bowel wall, and one (5.3%) had lymph node metastasis. At a median follow-up of 33.6 months, one patient (5.3%) developed local recurrence and subsequent distant metastasis. The minilaparotomy approach is suitable for an additional operation following colonoscopic polypectomy for T1 carcinoma, thus providing a minimally invasive alternative to conventional laparotomy.