The purpose of this study was to assess the accuracy of this tissue staining assessment of surgical specimens in delineating deep surgical margins in oral cancer surgery. Fifteen patients who underwent surgery for oral carcinoma were included in the study. Once the tumor was resected, a vertical section of the surgical specimen was taken from the central part of the tumor. The section was consecutively stained with 0.4% indigo carmine and 0.5% Congo red, and deep surgical margins were assessed using a digital microscope with a magnification power of 25-175x. The results of tissue staining analysis were compared with the corresponding results of conventional histopathological analysis with HE staining, which is considered the gold standard. The extent of carcinoma invasion could be visualized after the application of tissue staining solutions. Tissue staining analysis was accurate in 12 of the 15 patients (80%) in evaluating the closest deep surgical margin. There was no significant difference in the tumor-margin distance between tissue staining and histopathological assessment in these 12 patients (Wilcoxon signed-ranks test, P>0.63). The results of this study showed that intraoperative tissue staining of surgical specimens permitted visual inspection and assessment of tumor spread to surgical margin, although the method has some limitations. The method had a possible ability in controlling the deep surgical margin.