Aims: To determine antibacterial activity in lactic acid bacteria ( LAB) silage inoculants and in wheat and corn silages which were treated with these inoculants. Methods and Results: Wheat and two corn silages were prepared in 0(.)25 l sealed glass jars. Inoculant treatments were prepared for each type of silage with each of 10(6) LAB silage inoculants at inoculation rate of 10(6) CFU g(-1). Untreated silages served as controls. Antibacterial activity was determined in the inoculants and in their respective silages with Micrococcus luteus and Pseudomonas aeruginosa. Antibacterial activity was detected in nine of the 10 inoculants whereas such activity in the silages varied. Control silages did not have antibacterial activity. Conclusions: Many LAB silage inoculants have antibacterial activity and in some cases this activity is imparted on inoculated silages. Significance and Impact of the Study: This study was conducted as part of a broader research objective, which is to find out how LAB silage inoculants enhance ruminant performance. The results of this study indicate that LAB silage inoculants produce antibacterial activity, and therefore, have a potential to inhibit detrimental microorganisms in the silage or in the rumen.