This study evaluated the antimicrobial activity of Universal Bond II adhesive and two experimental versions of Universal Bond II adhesives against the bacteria, Streptococcus mutans. The zones of bacterial inhibition produced by three samples of the adhesive (identified as Batches 1, 2, and 3) were measured and compared. Batch 1 contained 0.7% glutaraldehyde, Batch 2 contained 1.0% glutaraldehyde, and Batch 3 contained 0.45% glutaraldehyde (current Universal Bond II adhesive). The bacteria was swabbed over the surface of agar plates in two directions. The plates were divided into the following two groups: Group I-Batches 1, 2, 3 were placed into wells for 1 minute before being cured. Group II-Batches 1, 2, 3 were placed into wells for 20 seconds before being cured. Zones of microbial inhibition were measured in millimeters at the end of 24, 48, and 72 hours. All batches of the adhesive produced zones of inhibition against S. mutans. All batches of the adhesive maintained zones of inhibition throughout the 72 hours of the study.