Students in this study were involved according to “Introduction to Clinical Practice Program” at Marmara University, School of Medicine, during 2003-2004 educational period. The aim of this study was to increase the students' knowledge and awareness about development of antimicrobial resistance in bacteria and acquire attitudes necessary for rational usage of antibiotics. Bacteroides species are the microorganisms most often isolated from patients with suppurative anaerobic infections and resistant to most of the antibiotics. In the present study, 3 cefoxitin -resistant Bacteroides fragilis mutants (two strains from stool specimens of different persons, one strain was ATCC Bacteroides fragilis) were obtained by selection with increasing concentrations of cefoxitin (ranging from subinhibitor concentration to 256μg/ml). The mutant strains showed decreased susceptibilities not only to cefoxitin but also to other antibiotics; two cefoxitin resistant mutants isolated from stool specimens showed resistance to tetracycline (64μg/ml) and intermediate resistance to piperacillin, ATCC strain showed resistance to clindamycin (8μg/ml) and 4-8 fold decreased susceptibilities to piperacillin and tetracyclin respectively. In conclusion, the students demonstrated that usega of antibiotics can encourage the selection of resistance and assumed that in order to minimize the potential development of resistance, rational use of antibiotic is critical.