Omiderm (Omikron Scientific Ltd., Rehovot, Israel), a new synthetic wound covering based on hydrophilized polyurethane, was found to be highly permeable to water. Values in the region of 5000 g/m2 24 h were found for the water permeability of Omiderm in comparison to 1400 and 500 g/m2 24 h for Biobrane (Hall, Woodroof Inc., Santa Ana, CA) and OP site (Smith and Nephew Ltd.), respectively. Permeabilities of antibacterial agents through Omiderm were found to be two to three orders of magnitude greater than those through Biobrane. The in vitro effectiveness of various antibacterial agents in lowering bacterial growth of different bacterial strains were applied to seeded agar plates through Omiderm membrane was investigated. NBH ointment (1% Neomycin, 1% Bacitracin, and 0.5% Hydrocortisone) was found to be the most effective material in inhibiting bacterial growth, except for Pseudomonas aeruginosa where silver sulfadiazine was superior. In in vivo experiments bacterial counts of infected wounds covered with Omiderm and topically treated with NBH were lowered to less than 10(3) organism/g tissue after one day of treatment.