PURPOSE. To investigate the anti-proliferative effect of A. blanchetti and A. schottii extracts. METHODS. The anti-proliferative effect of A. blanchetti and A. schottii ethanolic extracts on K562 leukemic cells as well as on BMEC and HUVEC were evaluated. Phytochemical analysis to identify the possible active components was carried out. RESULTS. The root extract of A. schottii was the most active of them. At 80 mu g/mL, the root extracts showed a cytostatic effect on K562, whereas at 400 mu g/mL, there was a strong cytotoxic effect. Similar cytostatic and cytotoxic effects were seen in the endothelial cells, but at lower doses. The effect of A. schottii root extract on endothelial cells was seen at concentrations ten times lower (8 mu g/mL) than the effect of the A. blanchetti root extract (80 mu g/mL). Phytochemical investigation of different fractions and parts of the plant led to the isolation of several known compounds, some of which are described for the first time in the genus Allamanda, and with previous evidence of anticancer and antitumoral properties. CONCLUSIONS. Our results suggest that both plants studied exhibit cytostatic and cytotoxic activity, but the most active compounds are located in the roots.92200208