Seventy three hydrolysable tannins and related compounds were isolated from seven Euphorbia plants. Among them, 28 compounds including nine gallotannins, eleven ellagitannins and eight related compounds were selected according to the structural similarity. Cytotoxicity of them on the human tumor cell lines including A-549, SK-OV-3, SK-MEL-2, XF-498 and HCT-15 were evaluated by the SRB method in vitro. 3,4,6-Tri-O-galloyl-D-glucose was shown to exhibit most potent cytotoxic effect($4.4{mu}g/ml