Shunji Yunoki,1 Masushi Kohta,2 Yoshimi Ohyabu,1 Tetsuji Iwasaki2 1Biotechnology Group, Tokyo Metropolitan Industrial Technology Research Institute, 2Medical Engineering Laboratory, ALCARECo., Ltd, Tokyo, Japan Purpose: This study evaluated the in vitro antibacterial activity and cytotoxicity of various commercially available silver-containing dressings (Ag dressing). Methods: Biohesive Ag (hydrocolloid, silver sulfadiazine), Aquacel® Ag (nonwoven fabric, ionic silver [Ag+]), Algisite™ Ag (nonwoven fabric, Ag+), Mepilex® Ag (foam, silver sulfate), and PolyMem® Ag (foam, nanocrystalline silver) were tested for characteristics of Ag+ release, antibacterial activity, and cytotoxicity. The release of Ag+ was investigated in cell culture medium at immersion periods of 6, 24, and 48 hours. The antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa were accessed by a disc diffusion test. The cytotoxicity was evaluated using V79 cells, by an extraction method. Results: The cytotoxicity was not a monotonic function of the antibacterial activity among the Ag dressings and could not be simply explained by Ag+-release properties. Biohesive Ag was regarded as a slow-release Ag dressing, showing the lowest cytotoxicity, while the antibacterial activity was classified as “strong” or “significant” against the two species of bacteria. Aquacel Ag and Algisite Ag showed higher antibacterial activity and cytotoxic effects, which were supported by the higher Ag+ release. Mepilex Ag showed the highest release of Ag+, and the cytotoxicity was the highest among the Ag dressings. However, the antibacterial activity was classified as “significant” or “no activity” for P. aeruginosa and S. aureus, respectively. PolyMem Ag showed the lowest Ag+ release, and the antibacterial activity classified as “significant" or "no activity” for S. aureus and P. aeruginosa, respectively, whereas the cytotoxicity was similar to those of Aquacel Ag and Algisite Ag. Conclusion: The efficacy and adverse effects of the Ag dressings revealed differences that should be considered by clinicians during wound management. Keywords: ionic silver, silver sulfadiazine, nanocrystalline silver, wound management, wound infection, slow release