Manufactured nanoparticles (NPs) can potentially cause negative effects on molecular (proteins and nucleic acids), subcellular, cellular, tissue, organ, and organism due to their unusual physicochemical characteristics. Ionizable NPs in water (e.g., Al2O3-NPs) may create toxic effects on aquatic animals. The present research determined the influences of Al2O3-NPs and appropriate concentrations of ionizing Al(III) using water-soluble AlCl(3)in zebrafish larvae (72 h post-fertilization,Danio rerio) by analyzing transcriptional alterations of stress-associated genes (rad51,p53,mt2) with quantitative real-time PCR (qRT-PCR). In addition, genotoxic effects of Al(III) and Al2O3-NPs were evaluated. The lethal concentrations that cause death of 50% (LC50) of zebrafish larvae when exposed to 0-50 mg/l Al(III) and 0-500 mg/l Al2O3-NPs were 3.26 +/- 0.38 and 130.19 +/- 5.59 mg/l, respectively, for 96 h. A concentration-dependent increase was observed in the genotoxicity in cells of larvae exposed to Al(III) and Al2O3-NPs for 96 h. DNA damage was more severe in larvae exposed to Al(III) (41.0% tail) than that of Al2O3-NPs (21.8% tail). A complex induction of stress-associated genes was observed in fish and this induction was not directly related to the concentrations of Al(III) and Al2O3-NPs, although a significant induction was detected inmt2gene of larvae exposed to Al(III) and Al2O3-NPs relative to control group. The induction levels ofmt2were 4.13 +/- 0.1 and 2.13 +/- 0.1-fold change (mean +/- S.E.M.) in larvae at 15 mg/l of Al(III) and 100 mg/l of Al2O3-NP concentrations, respectively.