The antimicrobial activity of 8 selenoorganic compounds (3-benzisoselenazoles, 1-benzisoselenazolone oxide and 4-disaryl diselenides) was investigated. It was found that selenoorganic compounds from benzisoselenazolone group suppress growth of some fungi and bacteria. The growth of Saccharomyces cerevisiae sigma 127-8b and Candida albicans 258 strains was strongly inhibited by the 2-(4-chlorophenyl)-1,2-benzisoselenazol-3(2H)-one. Also Ebselen and 2-acetyl-1,2-benzisoselenazol-3(2H)-one caused strong inhibition of Saccharomyces cerevisiae sigma 127-8b growth but a lower effect was observed in assays with Candida sp. strains. Benzisoselenazolones were also found to have antibacterial activities. They significantly reduced the growth of Gram-negative Escherichia coli K-12 ROW and Gram-positive Staphylococcus aureus 209P (Oxford) bacteria strains.