Amnesic shellfish poisoning toxin domoic acid (DA) is a marine neurotoxin that accumulates in fish and shellfish, and has been implicated to be involved in human and marine wildlife mortality. The transcriptional responses of cytochrome P-450 1A (CYP1A), glutathione S-transferase alpha (GSTA), glutathione S-transferase rho (GSTR), heat shock protein 70 (HSP70), and Na+/K+-ATPase alpha 1 (ATP1A1) in the liver of rabbitfish (Siganus oramin) intracoelomically injected with DA, were investigated. Experimental fish were administered with one injection of DA (2 μg/g wet weight) or PBS as control. After 24 h, fish were killed and hepatic RNA was isolated. Partial cDNA of rabbitfish CYP1A, GSTA, GSTR, HSP70, ATP1A1, and β-actin were obtained by PCR using degenerate primers. Using β-actin as an external control, the relative liver CYP1A, GSTA, GSTR, HSP70, and ATP1A1 mRNA abundance of rabbitfish were determined by semi-quantitative RT-PCR within the exponential phase. The ratio CYP1A/β-actin mRNA (%) of exposure group was determined to be 148.92 ± 12.69, whereas the ratio of control group was 82.3 ± 8.35, indicating that CYP1A was induced significantly in rabbitfish following DA exposure (P < 0.05). Although the expressions of GSTA, HSP70, and ATP1A1 tended to increase and GSTR tended to decrease, no significant changes were found (P > 0.05). The induction of hepatic CYP1A in response to DA suggests a potential role for fish phase I xenobiotic metabolizing enzyme in DA metabolism. © 2008 Wiley Periodicals, Inc. Environ Toxicol, 2008.