<div><p>Two new <i>ent</i>-atisanes <i>ent</i>-1β,3β,16β,17-tetrahydroxyatisane (<b>1</b>), <i>ent</i>-1β,3α,16β,17-tetrahydroxyatisane (<b>2</b>) together with 11 known diterpenes were isolated from the anti-tumour activity fraction of <i>Euphorbia fischeriana</i> Steud. The compounds were identified by detailed spectroscopic analysis, including extensive 2D-NMR experiments. X-ray analysis was applied to determine the structure of compound <b>2</b>. All 13 compounds were screened for cytotoxicity <i>in vitro</i> against human tumour MCF-7, HepG-2 and SGC-7901 cell lines. Compounds <b>1</b> and <b>2</b> showed the inhibitory effects against MCF-7 with IC<sub>50</sub> levels of 23.21 and 15.42 μM; simultaneously, compounds <b>4</b>, <b>6</b>, <b>8</b> and <b>11</b> also had definite inhibitory effect against different cell lines.</p></div
