In this work, we report the synthesis, structural characterization and evaluation of in vitro antioxidant and cytotoxic properties of novel spirobenzothiazolines (1a-e, 2a-e). 5-nonsubstituted spirobenzothiazolines (1a-e) demonstrated notable inhibitory capacity on lipid peroxidation (LPO), reducing power and scavinging effects on diphenylpicryl hydrazine (DPPH.) and 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid (ABTS. +) radicals, that were similar to that of alpha-tocopherol. The most potent antioxidant was compound 1a (incorporating an ethyl group on the cyclohexane ring) with an anti-LPO activity 2-fold higher than that of alpha-tocopherol. Compound 1a exhibited anti-LPO and DPPH. scavenging activities at concentrations lower than those cytotoxic for mouse normal fibroblast (NIH/3T3) cells and was also found to be slightly more selective for cancer cells (human prostat adenocarcinoma cell/PC-3) than normal mammalian cells.