After incorporation pharmacophores of allylamine and sulfanilamide into 4-thiazolidinone's ring - no antimicrobial activity was determined. This outcome stimulated synthesis of new group - 5-substituted 4-thiazolidinones. In the literature it is noted that the fragment of aldehyde in 5 position of 4-thiazolidinone's ring should give or increase biological activity. So, it was decided to incorporate fragment of aldehyde into 4-thiazolidinone's ring together with sulfanilamide pharmacophore, investigate antimicrobial activity and compare it with initial compounds - sulfanilamides. It was established that new compounds suppressed growth of S. arteus, E. coli, B. subtilis, P. mirabilis, C. albicans. Sulfanilamide, sulfapyridine and/or 2-chlorobenzaldehyde were incorporated into the structure of the most active compounds. It was concluded that synthesis of 4-thiazolidinones substituted by aldehyde in 5 position and sulfanilamide in 2 position are not potential antimicrobial agents.