In a retrospective study of 58 patients from all over Sweden, treated for small squamous cell carcinoma of the mobile tongue (T1N0M0), different prognostic factors were evaluated. A partial glossectomy was performed as primary treatment in all patients. The cancer recurred in 28 (38%) of 58 patients. One of 7 patients with only local recurrence, and 9 of 14 with recurrence in the neck died of their disease. The relative survival rate was 77%. Of the prognostic factors tested, tumor thickness was found to be the most significant. In patients with tumor thickness was found to be the most significant. In patients with tumor thickness exceeding 10 mm, recurrences occurred in 58% (P less than 0.0048), and 87% (P less than 0.0164) died of their cancer. This represents a statistically significant higher degree when compared with tumor thickness of less than 10 mm. Elective treatment of the neck nodes is recommended in epidermoid cancer of the mobile tongue when tumor thickness exceeds 10 mm, even in stage I tumors (i.e., the surface extension diameter is smaller than 20 mm at most).