In the antimicrobial therapy of denture stomatitis, it is desirable to inhibit the growth of not only the primary causative organism, Candida albicans, but also other oral bacteria closely associated with the condition. Three synthetic anti-candidal chalcones were characterized and compared for their additional activity in inhibiting these causative bacteria. Among the tested chalcones, 2,4,2'-trihydroxy-5'-methylchalcone showed the highest activity for different Gram-positive bacteria. It inhibited the growth of streptococci, staphylococci and lactobacilli at 25.0-50.0 micrograms/mL which was lower than or comparable to its minimum inhibitory concentration for candida. It functioned with a bactericidal action and leaked 260 nm-absorbing substances from the streptococcal cells. The antimicrobial activity of 2,4,2'-trihydroxy-5'-methylchalcone against both primary and secondary causative agents suggests it could be useful as a potent therapeutic agent in denture stomatitis.