A number of organic thiosulfates (Bunte salts) were prepared from appropriate primary bromides or iodides. In the case of substrates with long aliphatic chains, an addition of benzyltrimethylammonium chloride as phase transfer catalyst was very successful. The Bunte salts obtained were tested for antibacterial and fungicidal activity by means of the agar disc-diffusion method and by assignation of the minimum inhibitory concentrations (MIC). It was found that the microorganisms Proteus vulgaris, Candida albicans and Staphylococcus aureus showed the highest sensitivity. Biological activity of the compounds studied was dependent on the length of the aliphatic chain. Among the investigated compounds, aliphatic thiosulfates with 10-13 carbon atom chain were the most potent.