AIM: To evaluate the chemopreventive effects of aqueous Azadirachta indica (A indica) leaf extract (AAILE) against benzo(a)pyrene [B(a)P]-induced forestomach tumorigenesis in Balb/c mice. METHODS: Female Balb/c mice were divided into four groups of 10-12 animals each. For induction of forestomach tumors, starting from d 14 of the experiment, mice of B(a)P and B(a)P+A indica groups were given intra-gastric instillations of B(a)P (40 mg/kg), twice a week for four weeks. Mice of A indica and B(a)P+A indica groups were orally administered with AAILE (100 mg/kg), two weeks prior to B(a)P instillations till the end of the experiment. After 22 wk of the first B(a)P instillation, mice were sacrificed and the forestomachs were analyzed for development of tumors, scanning electron microscopy (SEM) and histopathology. RESULTS: Tumor incidence was observed to be 100% in mice that received only B(a)P. However, treatment with AAILE reduced the tumor incidence by 58.4% as observed in mice of B(a)P+A indica group when compared to that of B(a)P group. Similarly, the tumor burden and multiplicity were seen to decrease by 87.3% and 69.6% respectively in mice of B(a)P+A indica group when compared to those of B(a)P group. Scanning electron microscopy analysis showed that AAILE treatment itself did not cause any abnormalities on the surface architecture of forestomach epithelium. In tumorous forestomach, surface disruption was observed. Over the forestomach tumors of B(a)P group of mice certain rounded structures were seen in addition to closely placed tongue-shaped squamous cells. Interestingly, these rounded structures were not observed in B(a)P + A indica group of mice. Histopathalogically, the tumors were identical and diagnosed to be papillomas. Mice from control and A indica groups of mice did not develop any forestomach tumors and showed normal histo-architecture. CONCLUSION: The present data suggest that A indica exerts chemopreventive effects against B(a)P-induced forestomach tumors in murine model. Because of lack of toxicity and ubiquitous bioavailability, A indica may play a promising role in future drug discovery and development as far as chemoprevention of cancer is concerned. AIM: To evaluate the chemopreventive effects of aqueous Azadirachta indica (A indica) leaf extract (AAILE) against benzo (a) pyrene [B (a) P] -induced forestomach tumorigenesis in Balb / c mice. METHODS: Female Balb / c mice For induction of forestomach tumors, starting from d 14 of the experiment, mice of B (a) P and B (a) P + A indica groups were given intra-gastric instillations of Mice of A indica and B (a) P + A indica groups were orally administered with AAILE (100 mg / kg), two weeks prior to B (a) P (40 mg / kg) (a) P instillations till the end of the experiment. After 22 wk of the first B (a) P instillation, mice were sacrificed and the forestomachs were analyzed for development of tumors, scanning electron microscopy (SEM) and histopathology. RESULTS: Tumor incidence was observed to be 100% in mice that received only B (a) P. However, treatment with AAILE reduced the incidence of cancer by 58.4% as observed in mice of B (a) P + A Indica group when compared to that of B (a) P group. Similarly, the tumor burden and multiplicity were seen to decrease by 87.3% and 69.6% respectively in mice of B (a) P + A indica group when compared to those of B (a) P group. Scanning electron microscopy analysis showed that AAILE treatment itself did not cause any abnormalities on the surface architecture of forestomach epithelium. In tumorous forestomach, surface disruption was observed. Over the forestomach tumors of B (a) P group of mice certain rounded structures were seen in addition to closely placed tongue-shaped squamous cells. Interestingly, these rounded structures were not observed in B (a) P + A indica group of mice. Histopathalogically, the tumors were identical and diagnosed to be papillomas. Mice from control and A indica groups of mice did not develop any forestomach tumors and showed normal histo-architecture. CONCLUSION: The present data suggest that A indica exerts chemopreventive effects against B (a) P-induced forestomach tumors in murine model. Because of lack of toxicity and ubiquitous bioavailability, A indica may play a promising role in future drug discovery and development as far as chemoprevention of cancer is concerned.