Grapevine leaves are widely discarded in open fields despite their known antioxidant properties. We tested the cytotoxicity of leaf extracts from three clones (CL-260, CL-1048, CL-8) of Vitis vinifera L. cv. Tempranillo against four human cancer cell lines: colon, HT-29; breast, MCF-7; lung HTB-54; and lymphoblastic leukemia, CCRF-CEM. Grapevines were cultivated at either ambient (24/14 degrees C) or elevated (28/18 degrees C) day/night temperatures, and inoculated (+M) or not (-M) with arbuscular mycorrhizal fungi (AMF). Cytotoxicity was analysed by MTT assays. Elevated air temperatures enhanced the cytotoxicity of leaf extracts from CL-260 against HT-29, CCRF-CEM and HTB-54 and that from CL-8 against MCF-7. Mycorrhization improved the cytotoxicity of leaf extracts from CL-1048 against HT-29, CCRF-CEM, HTB-54 and MCF-7. The cytotoxic activities of CL-260 against HTB-54 and CL-1048 against HT-29 were correlated, respectively, with total phenols and total antioxidant capacity. We conclude that the predicted increase in air temperature for the future climate and the mycorrhizal association of grapevines may enhance the cytotoxicity of leaves, which strengthens the potential application of these agricultural residuals for biomedicine. However, the clonal diversity in the response to AMF and air temperature highlights the importance of choosing the most adequate clone for a concrete environmental scenario.