The fractionation, guided by cell-growth inhibition assay, of the EtOAc crude extract from grape stems of the Sicilian Vitis vinifera variety 'Nerello Mascalese' allowed identification often constituents, isolated either as pure compounds (1, 3-5, 7-10) or inseparable mixtures (2a-d and 6a-e). The pure constituents were: two triterpenoid acids, oleanolic (1) and betulinic acids (5); daucosterol (7); a stilbenoid, E-resveratrol (3) and its dimer E-epsilon-viniferin (4); the simple phenol gallic acid (8); and the flavanols catechin (9) and gallocatechin (10). Four 6'-O-acyldaucosterols (2a-d) and five 1,2-di-O-acyl-3-O-beta-D-galactopyranosyl glycerols (6a-e) were also identified as inseparable mixtures. All the isolated compounds were subjected to spectroscopic analysis and MTT bioassay on MCF-7 human breast cancer cells. The majority showed growth-inhibitory activity, 5 being the most active (GI50 = 0.57 microM). Compounds 3-5 were also tested on HT-29, U-87-MG and U-373-MG cell lines.