Abstract Background: The rapid emergence of antibiotic resistance is a result of human use of antibiotics in medicine and agriculture. There are a few reports suggest that antibiotic resistance will be reversed in the absence of antimicrobial use. In this study we investigate whether acquired resistance might disappear by reducing the volume of antibiotic use.Materials and methods: In this study we analyzed one hundred and twenty five blood culture E.coli isolates. These isolates were obtained from the diagnostic microbiology laboratory of the Rikshospitalet, Oslo University Hospital. Minimum inhibitory concentrations (MICs) were determined by Etest (AB Biodisk, Solna, Sweden).Results: Our results show that antibiotic resistances to sulphonamide, amphenicols, tetracyclines, streptomycin and gentamycin are increasing despite restrictions on use of antibiotics in Norway. Exception is resistance to kanamycin where all strains were susceptible in this study.Conclussion: Our present study shows that restriction on antibiotic use does not necessarily reduce resistance within a few decades. The genetic linkage of the resistance to other determinants is the main reason for this phenomenon.