The following variants of E. coli resistant to tetracycline have been obtained from a strain of E. coli W-677 susceptible to 2.5 mcg/ml of the antibiotic: Ri, a recombinant resulting from crossing E. coli W-677 (recipient) and E. coli CSH-222 (donor), resistant to 200 mcg/ml of tetracycline; R2, a strain isolated upon numeros passaging E. coli W-677 on media containing the antibiotic, resistant to 25 mcg/ml of tetracycline. The ability of the resistant variants to bind the antibiotic decreased, as was found in experiments with 14C-tetracycline. Preincubation with low concentrations of the antibiotic resulted in an additional decrease of the sorption by the resistant variants, and in a decrease by 15--18 per cent in the case of the susceptible culture. The R2 variant differed in lipid composition from the parent, susceptible culture: it contained less total lipids and unsaturated fatty acids, and more branched fatty acids. The R1 variant hardly differed in lipid composition from the susceptible culture.