In this paper, the antibacterial activity against Bacillus pumilus, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa of the wool fabrics treated with new antimicrobial bis-quaternary surfactants, DABK and DABB, is studied. The activity was established on the basis of the agar diffusion and protective antibacterial test results and on the basis of scanning electron microscopy (SEM) observation. The results were compared with the HTAB, a monoquaternary surfactant of conventional use. The results from the agar diffusion and protective antibacterial tests do not enable us to confirm whether these compounds are potentially useful antimicrobial agents for the protection of textiles. However, SEM observations show clearly the efficacy of these compounds to protect the wool fabrics against the micro-organisms. SEM has been a useful technique for the assessment of antibacterial activity in textiles.