Escherichia coli strains isolated from children with urinary tract infections (UTI) were investigated for their sensitivity to antimicrobial drugs, bacteriophages and bactericidal activity of human serum. It has been proved, that the resistance to bactericidal effect of serum is not the dominant feature of uropathogenic Escherichia coli strains. Significant percentage of the strains appeared to be sensitive to the most popular drugs ordered during UTI treatment in children. No simple relationship between sensitivity of the strains to the drug and to the human serum has been found. Three of 44 bacteriophages specific to Escherichia coli have shown the lytic effect towards 50-60% strains under investigations.