Several chalcones were synthesized and their in vitro cytotoxicity against various human cell lines, including human breast adenocarcinoma cell line MCF-7, human lung adenocarcinoma cell line A549, human prostate cancer cell line PC3, human adenocarcinoma cell line HT-29 (colorectal cancer) and human normal liver cell line WRL-68 was evaluated. Most of the compounds being active cytotoxic agents, four of them with minimal IC₅₀ values were chosen and studied in detail with MCF-7 cells. The compounds 1, 5, 23, and 25 were capable in eliciting apoptosis in MCF-7 cells as shown by multiparameter cytotoxicity assay and caspase-3/7, -8, and -9 activities (p < 0.05). The ROS level showed 1.3-fold increase (p < 0.05) at the low concentrations used and thus it was concluded that the compounds increased the ROS level eventually leading to apoptosis in MCF-7 cells through intrinsic as well as extrinsic pathways.