Taking into account the competitive action of zinc towards other ion essential for pathogenic germs metabolism, the complex erythromycin-zinc, zinc salts of sulfamethoxydiazine, sulfanilamide, sulfacetimide, sulfathiazole as well as the Mannich basis of sulfamethoxydiazine were synthetized. The antimicrobial action towards gram-positive, gram-negative pathogens and fungi was tested by the classic diffusiometric method. An increased antimicrobial action for the Mannich basis of sulfamethoxydiazine and for the zinc salt of sulfamethoxydiazine, alone or in association with metronidazole--chemotherapeutic agent used in the infections with anaerobic organisms was found. A significant antimicrobial action was also found for the complex erythromycin-zinc and zinc salts of sulfacetimide and sulfathiazole.