The present invention relates to substituted 5-aryl-2-aminoimidiazole compounds being active against microbial biofilm formation. The invention also relates to compositions comprising a microbial biofilm inhibiting amount of said substituted 5-aryl-2-aminoimidiazole compounds in combination with excipients. Methods for inhibiting or controlling microbial biofilm formation in a plant, a body part of a human or an animal, or a surface with which a human or an animal may come into contact are also disclosed.