A novel series of N'-[(3-Substituted alkyl/aryl)-4-oxo-1,3-thiazolidin-2-ylidene]-4-hydroxybenzohydrazide (4.a-4.m) compounds were synthesised. The compounds were tested for its toxicity (in vivo). The cut off LD50 were found ≥ 1000 mg/kg. Anticancer activity of these compounds was performed In vitro by cell proliferation assay using 3- (4,5-dimethylthiazol-2yl)-2, 5-diphenyltetrazolium bromide (MTT) staining method. Cell lines (A-549), Adeno carcinomic human alveolar basal epithelial cell line is used for screening. The compds, (6.h), (6.i), (6.k), (6.l) and (6.m), showed significant anticancer activity as percent cell lysis <75 to 100. Other compounds also exhibited promising anticancer activity.