The intense use and misuse of antibiotics are undoubtedly the major forces associated with the high numbers of resistant pathogenic and commensal bacteria worldwide. Both the volume and the way antibiotics are applied contributes to the selection of resistant strains. Still, other social, ecological and genetic factors affect a direct relationship between use and frequency of resistance. Resistant bacteria, following their emergence and evolution in the presence of antibiotics, appear to acquire a 'life of their own'. They proliferate and maintain the resistance traits even in the absence of antibiotics, thus jeopardizing the reversal of bacterial resistance by simple reduction in antibiotic use. Reversing resistance requires restoration of the former susceptible flora in people and in the environment. Copyright 2000 Harcourt Publishers Ltd.