Objective of the study was evaluation of the harmful effect induced by aluminum silicate in bone marrow chromosomes and liver tissues. Also, how could prevents this toxicity. 60 Adult male albino rats weighing 100-120 g were used for our experiments. The animals were divided into six equal groups: first normal healthy control group, second group was given 200 ml propolis/Kg day after day by stomach gavage, third group received low dose of aluminum silicate (5 mg/kg; intra peritoneal) twice a week, forth group injected with high dose of aluminum silicate (20 mg/kg; intra peritoneal) twice a week, fifth group received propolis and aluminum silicate with similar doses as that of second & third groups and sixth group received propolis and aluminum silicate with similar doses as that of second & forth groups. At the end of 8 weeks for each rat, bone marrow was aspirated and liver was removed for lab examinations. The results showed that rats exposed to aluminum silicate had severe chromosomal aberrations and changes in CYP gene expression. It caused significantly increased in the frequency of chromosomal aberrations such as polyploidy, hypoploidy, deletions, fragments, chromatid breaks, chromosome breaks, double minutes, ring, gap and translocation were also observed. Gene expression of CYPs was increased with exposure to aluminum silicate and was down regulated in