In this study, we evaluated the antiproliferative activity on two human osteosarcoma cell lines (MG-63 and Saos2) of oleuropein, an olive oil compound traditionally found in the Mediterranean diet. Oleuropein exhibited obvious cytotoxic effects on human osteosarcoma cells in a concentration- and time-dependent manner. Statistical analysis of IC50 by the Probit regression method suggested that oleuropein had similar toxic effects on both cell lines tested (IC50 range from 247.4-475.0 µM for MG63 cells and from 798.7-359.9 µM for Saos2 cells).