The antibacterial activity of coffee depends mainly on the degree of roasting of the coffee beans. To identify easily determinable chemical markers which relate to coffee's antibacterial activity, 5-caffeoylquinic acid, caffeic acid, nicotinic acid, trigonelline, 5-(hydroxymethyl)furfuraldehyde, the content of which changed throughout the roasting process, and caffeine were considered. A new HPLC method that allows determination of these compounds simultaneously was developed. Two antibacterial activity chemical markers were found: (1) the sum of trigonelline and nicotinic acid contents and (2) the 5-caffeoylquinic acid/caffeine ratio