BACKGROUND: The goal of this prospective study was to determine the frequency of micrometastases in patients with squamous cell carcinoma (SCC) of the oral cavity, pharynx and larynx in whom elective neck dissection was indicated (cN0). PATIENTS AND METHODS: A total of 12 patients (10 males and 2 females) were enrolled in the study. The age ranged 42-73 years (median 62 years). Elective neck dissection was performed in all patients (8 ipsilateral, 4 bilateral) and a total of 256 lymph nodes were removed and sent for microscopic examination. RESULTS: The presence of tumor cells in cervical lymph nodes was found in 5/12 (42%) patients. Micrometastases of SCC were found in two patients and isolated tumor cells (ITC) in two other patients. In the remaining one patient with oropharyngeal SCC, a micrometastasis of papillary thyroid carcinoma (PTC) was detected. Positive lymph nodes were localized in level II in three patients with SCC of larynx, hypopharynx and tongue base, respectively, in level I in one patient with SCC of oral tongue and in level III in one patient with PTC. CONCLUSION: Our results indicate that SCC of head and neck has a high potential for creating micrometastases which frequency is higher compared to clinically detected macrometastases. Therefore, elective neck dissection or radiotherapy of the neck should be considered in patients with high risk of occult metastases or micrometastases. and P. Čelakovský, D. Kalfeřt, K. Smatanová, V. Chrobok, J. Laco