With the purpose of demonstrating the presence of different types of cells in the syncytial and cytotrophoblast of the human placenta, a new technique of cell isolation was performed by utilizing a light enzymatic digestion and a separation on density gradients. Normal human placentas of the first trimester of pregnancy have been studied. After an accurate and light washing in saline and anticoagulant substances, whole villi have been incubated in a trypsin solution for various periods of time at 40 degrees C in a thermostatic stirrer. Detached cells have been collected, rinsed and separated by means of different density gradients of Percoll (d = 1.038 and 1.080). Three cellular layers have been collected and processed for the studies at light and electron microscopy. The first layer was mostly composed by multinucleated elements with a morphological pattern closely related to the histological characteristics of the syncytiotrophoblast; the second fraction was composed by mononucleated elements with the structural findings of the Langhans' cells; the third layer was represented almost exclusively by blood cells. The obtained results demonstrated the high utility and accuracy of the suggested method of cell isolation.