The authors investigated the incidence of transferable resistance in bacterial strains resistant to cephalosporins of the first and second generation in the course of two years in materials of the microbiological department of one of the larger district hygiene stations. They recorded the development of the first strains resistant also to cephamandol, although this antibiotic is not used at all in the above area, and in exceptional instances also resistance to cephotaxime. It was revealed that the transferable resistance to cephamandol is due to the presence of an enzyme which hydrolyzes this antibiotic. When using cephalosporins of the first generation, it is important to foresee an increasing incidence of transmitted resistance to these antibiotics and possibly some strains resistant also to cephalosporins of the second generation and in exceptional cases strains resistant to cephalosporins of the third generation.