OBJECTIVE The aim of this preliminary retrospective study was to evaluate the prognostic value of tumor thickness in squamous cell carcinoma of the floor of the mouth. MATERIALS AND METHODS A total of 61 patients with previously untreated T1N0, T2N0 or T3N0 squamous cell carcinoma of the floor of the mouth were included in this preliminary study. An optical micrometer was used to determine the maximum of tumor thickness. We studied the relation between the overall survival at two and five years and tumor thickness. RESULTS The cohort comprised 52 male and nine female patients. The mean and the median thickness were 7.2 and 6mm, respectively. Overall survival was 79.5 and 36.7% at two and five years, respectively. There was no significant association between thickness and overall survival (p=0.71) and between thickness and disease-free survival (p=0.63). CONCLUSION The prognostic value of tumor thickness was not demonstrated in this preliminary study. We are currently conducting a study involving a larger patient population in our unit and we believe that tumor thickness should be considered in the management plan for patients with oral carcinoma.