The different analogues of ebselen-unsubstituted benzisoselenazol-3(2H)-one (2a) 2-pyridylbenzisoselenazol-3(2H)-ones (2b-h) and 7-azabenzisoselenazol-3(2H)-ones (3a-j) were designed as new selenium-containing antiviral and antimicrobial agents and synthesized. Some of them were found in the antiviral assay in vitro to be strong inhibitors of cythopatic activity of herpes simplex virus type 1--HSV-1 (compounds 2a,b,f,h, 3a-j) and encephalomyocarditis virus--EMCV (compounds 2a,h, 3a-f,k,l). The compounds 2a,h and 3a-e,j were found to have an appreciable activity against Gram-positive bacteria (Staphylococcus aureus and Bacillus) in vitro, some of them inhibited growth of pathogenic yeasts (Candida albicans) (3a,b) and filamentous fungi (3a-e,f).