Heterocyclic amines (HCAs) are suspected human carcinogens formed in muscle foods during high temperature grilling or cooking. Inhibition of HCAs by commercial marinades rich in polyphenolic antioxidant containing spices was evaluated with beef round steaks cooked at 204 degrees C (400 degrees F). Treatment effects on the levels of 4 HCAs were investigated: 2-amino-3,8-dimethylimidazo[4,5-flquinoxaline (MeIQx), 2-amino-1-methyl-6-phenyl-imidazo[4,5-b]pyridine (PhIP), 1-methyl-9H-pyrido[4,3-b]indol (harman), and 9H-pyrido[4,3-blindol (norharman). The marinades were formulated according to the package label instruction in an oil, water, and vinegar mixture, and the steaks were treated for 1 h prior to grilling. All 3 marinades, Caribbean, Southwest, and herb, significantly decreased the imidazo-azaarene HCAs (MeIQx, PhIP) as contrasted to controls and liquid blanks. The Caribbean mixture showed the highest decrease in the total HCA content (88%), followed by the herb (72%) and Southwest (57%). With a few exceptions there were significant decreases in HCAs for treatments with only the marinade bases (ingredients without any spices/herbs). As measured by high-performance liquid chromatography (HPLC), the marinades contained considerable amounts of the polyphenolic antioxidants carnosic acid, carnosol, and rosmarinic acid with Caribbean being the highest. Commonly available spice-containing marinades can be effective inhibitors of HCA formation and provide reduced exposure to some of the carcinogens formed during grilling.