The mutans group of streptococci is considered to play a key role in the etiology of dental caries. We have evaluated the ability of different substances to prevent dental plaque formation without affecting Streptococcus sobrinus viability. Viable organisms were detected as CFU/mL in agar plates and bacterial adherence was assessed by dry weight. We studied 23 compounds and we demonstrated that phenyl salicylate, phenylmercuric nitrate and potassium iodate are more effective to inhibit adhesion without showing antibacterial activity.