Our experimental cryb (cryptochrome defective) mutant flies were segregated into four groups. Group I - control, group II - treated with 0.01% NDEA via culture medium for 21 days, group III- administered with NDEA, and vanillic acid (0.01%) and group IV - with vanillic acid. Behavioral irregularities in taste chemotaxis, geotaxis, thermotaxis, phototaxis, chemotaxis and hygrotaxis were quantitatively observed in NDEA administered cryb flies but were found to be near normal in vanillic acid administered flies. The levels of protein thiol, protein carbonyl, lipid peroxides and thiobarbituric acid reactive substances (TBARS) were significantly increased in NDEA administered flies and in the same way have a tendency to stabilize to normal level in vanillic acid treated groups; reduced glutathione (GSH), superoxide dismutase (SOD), glutathione-S-transferase (GST), catalase (CAT), glutathione peroxidase (GPx), and were diminished in NDEA administered group, and were noticeably elevated in vanillic acid administered groups. Histopathological studies of intestine and brain indicate the tumor in NDEA treated flies and vanillic acid tend to normalize the cellular architecture. Vanillic acid, a biologically active phytoconstituent is known to possess antiproliferative and antioxidant properties and our study indicates that this could prevent the process of carcinogenesis in cryb mutant of Drosophila melanogaster.