In an epidemiological study ,of enteropa~hogenic Escherichia coli, 102 strains were isolated from patients seen at the University Teaching Hospital in Lagos. The most c o m m o n serotype encountered was 055 followed by 026. Antimicrobial susceptibility testing and plasmid profiling of the strains were done. All the strains were sensitive to colistin, nalidixic acid, nitrofurantoin, cefotaxime, amikacin, and augmentin. Of the 102 strains, 47 (46%) were resistant to one or more of the following antimicrobial agents: Co-trimoxazole, tetracycline, ampicillin, streptomycin, sulphonamide and a combination of ampicillin with sulbactam. All the strains that were resistant to any antimicrobial agents were also resistant to ~etracycline. Seventy-t~wo strains (70.6%) h a r b o r e d plasmid whose molecular weights ranged from 0.8 to 120Γ10 a daltons. The m a j o r i t y of the plasmid were smaller than 6Γ10a; 90% of strains carrying plasmid ranging in size from 2 to 6Γ 10 a daltons and 50 t,o 70Γ 10 a daltons were resistant to one or more antimicrobial agents. Trasformation and conjugation experiment showed that about 57% of the resistant strains carried R plasmid. Plasmid-determined resistance to tetracycline, ampicillin, streptomycin and sulphonamide was found.