The antimicrobial activity of mercurius cyanatus complex (Oligoplex) and its components Mercurius cyanatus D5, Echinacea angustifolia D1, Ailanthus glandulosa D3, Ammonium bromatum D3, Baptisia tinctoria D3, Euspongia officinalis D2, alcohol 5% (dilution: D1 = 1: 10, D2 = 1 : 100 etc.) was tested in vitro by serial dilution tests against 105 clinical isolates (grampositive/negative, aerobes and anaerobes with relevance for pharyngitis). The bactericidal activity was compared with that of vancomycin when appropriate. One component of the composition (Mercurius cyanatus) exerted a considerable bactericidal activity against S. pyogenes, S. agalactiae, S. pneumoniae, S. aureus, E. faecalis in serial dilutions of the clinical relevant concentration D5. However, growth of H. influenzae, Bacteriodes sp. and Actinobacillus actinomycetemcomitans was not inhibited by Mercurius cyanatus and any other component of the composition. The composition, however, exerted a bactericidal range similar to that of Mercurius cyanatus, but less efficient. Analysis of the bactericidal effect of Mercurius cyanatus and vancomycin revealed comparability for S. pyogenes, S. agalactiae, S. pneumoniae, S. aureus and E. faecalis for vancomycin concentrations of 0.063-2 mg/l, which are clinically relevant.