Background: Detection of micrometastases in sentinel lymph nodes (SLN) extends our knowledge of lymphatic spread in endometrial cancer, although its clinical significance has not yet been confirmed. Objectives: The aim of study was to determine the incidence of SLN micrometastases and to analyze the association between micrometastases and disease relapse. Material and methods: Fifty-four patients with endometrioid endometrial cancer underwent routine surgical therapy and sentinel lymph node biopsy (SLNB). SLNB was performed using two techniques: cervical injection of 99mTc-labelled albumin or blue dye and fundal injection of blue dye. SLNs were subjected to ultrastaging with immunohistochemistry (AE1/AE3, 150μm). Results: At least one SLN was detected in 51 patients (94.4%) and bilateral SLN detection was achieved in 80.4%. Nodal macrometastases were found in 3 patients (6.3%). SLNB enabled us to detect nodal macrometastases in 2 out of those 3 patients. In the third case, detection of SLN micrometastasis allowed to correctly determine the nodal status, thus avoiding the false negative result of SLNB. In 48 patients with detected 184 SLNs, there were 4 patients (8.3%) with micrometastases and 4 (8.3%) with ITC foci. No significant associations between the presence of risk factors (grade, myometrial invasion, cervical invasion, lymphovascular space invasion) and incidence of micrometastases and/or ITC foci in SLNs were found. Conclusions: Detection of micrometastases may result in lower false-negative rate, thus increasing SLNB safety.