Three dogs with advanced-stage adenocarcinoma of the gastrointestinal tract were treated by use of resection, adjuvant chemotherapy with cisplatin and 5-fluorouracil, and second-look laparotomy (SLL). In combination with histologic examination of biopsy specimens obtained during the procedure, SLL is the most accurate diagnostic procedure for identification of residual or recurrent microscopic or macroscopic abdominal neoplasia; however, to the authors' knowledge, there are no reports of its clinical use in the field of veterinary oncology. This lack of clinical use in animals is likely because of factors such as cost, procedure-associated risks perceived by the owners and veterinarians, lack of data to define proper clinical application, and, perhaps to some degree, an entrenched belief that treatment of advanced stage cancer in animals is inappropriate. Nevertheless, the use of SLL should be considered for evaluation of abdominal tumors or intra-abdominal metastases in dogs that appear to be in complete clinical remission near or at the anticipated completion of chemotherapy (especially if effective second-line chemotherapy protocols are available) or when secondary cytoreduction might be beneficial.