Abstract: Amount of benzaldehyde migrated from food-contacting materials (e.g., polystyrene) into 4 simulated food mediums (i.e., 3 water-based mediums and 1 fat-based medium) was determined by HPLC. In case of water-based food, 3 portions of polystyrene sample were refluxed separately in the 3 simulated mediums at 95 ℃ for 2 h, and each of the extracts was made up to 100.0 mL with the respective water-based food medium, and used for HPLC analysis. In case of fat-based food, sunflower seed oil was taken as simulated food medium, and the polystyrene sample was soaked in the oil at 95 ℃ for 2 h in a tightly stoppered conical flask. Five grams of the cooled oil were taken, mixed with 10 mL of methanol and centrifuged for 5 min. The supernatant was transferred to a 25 mL volumetric flask. The lower layer was extracted twice with methanol and the supernatants were combined and made up to 25 mL with methanol, which was used for HPLC analysis also. Diamonsil C18 column was used as the stationary phase and a mixture of acetonitrile and PBS of pH 6.5 (75+25) was used as mobile phase. Detection at 245 nm was adopted in the determination. Lower limits of determination (10S/N) found for the 3 water-based food mediums were same as 0.01 mg·L-1, and for sunflower seed oil was 0.1 mg·kg-1. Values of recovery found were in the range of 89.1%-97.9%, with RSD′s (n=9) ranged from 2.6% to 7.9%.