In an investigation carried out over a period of six months, 53 strains of Enterobacteriaceae and nine strains of Pseudomonas aeruginosa were examined for antibiotic resistance and transmissible drug resistance factor. Seventeen antibiotic resistance patterns were found among 51 drug resistant Enterobacteriaceae. Of the 62 strains, 23 were capable of transferring a part or all of the antibiotic resistance pattern to sensitive Escherichia coli. The P aeruginosa isolated from both man and piglets harboured R-factors which were transferable at high frequencies to the sensitive recipients, while only one of the six single resistant E coli isolated from piglets transferred resistance to the sensitive recipients. The minimum inhibitory concentrations of oxytetracycline, ampicillin, chloramphenicol, sulphadimidine and streptomycin of the resistant E coli, P aeruginosa, Salmonella spp and Proteus spp were 500 to 625, 62 to 500, 500 to 625, 500 and 7.8 to 500 micrograms/ml, respectively.