Amniotic membranes are widely used in a multitude of surgical applications and have been shown to reduce bacterial counts and promote healing in infected wounds. Antibacterial properties of amniotic fluid are well documented and the presence of many potentially antibacterial factors has been demonstrated. No such factors have yet been found in amniotic membranes. We have applied a direct disc-diffusion susceptibility test to try to establish the possible existence of such a factor. Amniotic membranes did not inhibit five bacterial species when tested at 3 X 10(6) and 3 X 10(8) colony forming units/ml. However, complete growth inhibition of all organisms was seen immediately under the amniotic membrane discs. These results support the hypothesis that the antimicrobial effect of amniotic membranes in vitro is due to their close adherence to the wound surface.