Styrene dimers and trimers in polystyrene were extracted with cyclohexane-2-propanol (1:1) and determined by GC-FID. The analyzed samples were disposable cups, food cases, bowls, trays, cases of yogurt and tofu, and cups of instant noodles, chow mein, spaghetti, etc. All samples contained the dimers and trimers and residue levels were 90-1, 030μg/g (average 380μg/g) and 650-20, 770μg/g (average 9, 210μg/g), respectively. The cyclotrimer, 1-phenyl-4-(1′-phenylethyl) tetralin, accounted for about two-thirds of the residues. The migration test with food simulated-solvents was carried out using three types of polystyrenes containing about 10, 000μg/g of dimers and trimers. High-impact polystyrene released larger amounts of dimers and trimers than general-purpose polystyrene and the migration levels into n-heptane were 44.8μg/cm² and 0.38μg/cm², respectively.