Hydrosols that contain silver nanoparticles with average particle sizes of 10-15 and 20-25 nm have been synthesized using chemical reduction. The antimicrobial activity with respect to the Gram-negative bacteria Escherichia coli ML35p and Pseudomonas aeruginosa ATCC 27853, the antibiotic-resistant clinical isolate of Pseudomonas aeruginosa, and the Gram-positive bacteria Staphylococci aureus SG511 and Listeria monocytogenes EGD, as well as the hemolytic activity of the synthesized samples, has been investigated. The results obtained have shown that the use of the samples under investigation for the development of new bactericides holds promise.