Both nitrofurantoin-sensitive and nitrofurantoin-resistant strains of Vibrio el tor were found to lyze in the presence of Tris-EDTA at alkaline pH. The rate of lysis was appreciably enhanced by lysozyme. The amounts of intracellular components, viz. proteins and carbohydrates, released from the nitrofurantoin-sensitive strain by Tris-EDTA treatment, were significantly lower than those from the nitrofurantoin-resistant strain. Differences in periplasmic proteins released from Tris-EDTA treated cells of nitrofurantoin-resistant and -sensitive strains were revealed by gel electrophoresis. © 1983 Institute of Microbiology, Academy of Sciences of the Czech Republic.