The antimicrobial effects of rhizophora apiculata pyroligneous acid on pathogenic microorganisms were evaluated. Pyroligneous acid (PA) and concentrated pyroligneous acid (CPA) showed various levels of antimicrobial activity against 14 species of microorganisms (10 species of bacteria 2 species of yeasts and 2 species of fungi) with bacteria as the most susceptible microorganisms. The bio-active component (s) of PA was isolalated using dicho