In this study, 5-chloro-3H-spiro-[1,3-benzothiazole-2,3'-indole]-2'(1'H)-one derivatives 3a-l were synthesized by the reaction of 1H-indole-2,3-diones 1a-l with 2-amino-4-chlorothiophenol 2 in ethanol. 3a-l were tested for their abilities to inhibit lipid peroxidation (LP), scavenge DPPH center dot and ABTS(center dot+) radicals, and to reduce Fe3+ to Fe2+. Most of the tested compounds exhibited potent scavenging activities against ABTS(center dot+) radical, reducing powers and strong inhibitory capacity on LP. 3a, 3d, 3e, 3h, 3j and 3k chosen as prototypes were evaluated in the National Cancer Institute's in vitro primary anticancer assay. The greatest growth inhibitions were observed against a non-small cell lung cancer cell line HOP-92 for R-1-fluoro substituted 3d and a renal cancer cell line RXF-393 for R-chloro substituted 3e in the primary screen.